Quarterly report pursuant to Section 13 or 15(d)

FAIR VALUES OF ASSETS AND LIABILITIES - Level 3 Classification of Gains/Losses (Details)

v3.10.0.1
FAIR VALUES OF ASSETS AND LIABILITIES - Level 3 Classification of Gains/Losses (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Dec. 31, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]          
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included in Earnings     $ 25 $ 9  
MSRs          
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]          
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings $ 0 $ (1) 0 (2)  
Mortgage banking income 0 1      
Securities gains (losses)   0      
Other expense 0        
Fair Value, Assets and Liabilities Measured on Recurring Basis, Gain (Loss) Included in Earnings 0 (1)      
Fair Value Assets Measured On Recurring Basis Gain Loss Included In Interest and fee income   0      
Derivative Financial Instruments          
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]          
Mortgage banking income (9) (1)      
Securities gains (losses)   0      
Other expense 0        
Fair Value, Assets and Liabilities Measured on Recurring Basis, Gain (Loss) Included in Earnings (9) (1)      
Fair Value Assets Measured On Recurring Basis Gain Loss Included In Interest and fee income   0      
Municipal securities          
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]          
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings (1) (1) (3) (4)  
Mortgage banking income 0 0      
Securities gains (losses)   0      
Other expense (1)   (3)    
Fair Value, Assets and Liabilities Measured on Recurring Basis, Gain (Loss) Included in Earnings (1) (1)      
Fair Value Assets Measured On Recurring Basis Gain Loss Included In Interest and fee income   (1)      
Asset-backed securities          
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]          
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings   (2) (2) (5)  
Mortgage banking income   0      
Securities gains (losses)   (2)      
Fair Value, Assets and Liabilities Measured on Recurring Basis, Gain (Loss) Included in Earnings   (2)      
Fair Value Assets Measured On Recurring Basis Gain Loss Included In Interest and fee income   0      
Automobile          
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]          
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings 0 0 0 (1)  
Mortgage banking income 0 0      
Securities gains (losses)   0      
Other expense 0        
Fair Value, Assets and Liabilities Measured on Recurring Basis, Gain (Loss) Included in Earnings $ 0 0      
Fair Value Assets Measured On Recurring Basis Gain Loss Included In Interest and fee income   $ 0      
Mortgage Banking Income [Member]          
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]          
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included in Earnings     25 9  
Mortgage Banking Income [Member] | MSRs          
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]          
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings     0 (2)  
Mortgage Banking Income [Member] | Municipal securities          
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]          
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings     0 0  
Mortgage Banking Income [Member] | Asset-backed securities          
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]          
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings     0 0  
Mortgage Banking Income [Member] | Automobile          
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]          
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings     0 0  
Securities Gain (Losses) [Member]          
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]          
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included in Earnings     0 0  
Securities Gain (Losses) [Member] | MSRs          
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]          
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings     0 0  
Securities Gain (Losses) [Member] | Municipal securities          
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]          
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings     0 0  
Securities Gain (Losses) [Member] | Asset-backed securities          
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]          
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings     (2) (5)  
Securities Gain (Losses) [Member] | Automobile          
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]          
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings     $ 0 0  
Noninterest Income          
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]          
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included in Earnings       0  
Noninterest Income | MSRs          
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]          
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings       0  
Noninterest Income | Municipal securities          
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]          
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings       0  
Noninterest Income | Asset-backed securities          
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]          
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings       0  
Noninterest Income | Automobile          
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]          
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings       $ (1)  
Interest and Fee Income [Member]          
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]          
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included in Earnings         $ 0
Interest and Fee Income [Member] | MSRs          
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]          
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings         0
Interest and Fee Income [Member] | Municipal securities          
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]          
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings         (4)
Interest and Fee Income [Member] | Asset-backed securities          
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]          
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings         0
Interest and Fee Income [Member] | Automobile          
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]          
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings         $ 0