Annual report pursuant to Section 13 and 15(d)

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

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FAIR VALUES OF ASSETS AND LIABILITIES - Level 3 Classification of Gains/Losses (Details) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Dec. 31, 2018
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Net derivatives gain (loss) included in earnings $ 35 $ 35 $ 16 $ (1)
MSRs        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Assets gain (loss) included in earnings (1) (1) (3) (4)
Municipal securities        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Assets gain (loss) included in earnings (3) (3) (2) 7
Asset-backed securities        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Assets gain (loss) included in earnings (2) (2) (5) (2)
Automobile        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Assets gain (loss) included in earnings $ 0   1 (2)
Mortgage banking income        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Net derivatives gain (loss) included in earnings   35 16 (1)
Mortgage banking income | MSRs        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Assets gain (loss) included in earnings   (1) (3) (4)
Mortgage banking income | Municipal securities        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Assets gain (loss) included in earnings   0 0 0
Mortgage banking income | Asset-backed securities        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Assets gain (loss) included in earnings   0 0 0
Mortgage banking income | Automobile        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Assets gain (loss) included in earnings     0 0
Securities gains (losses)        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Net derivatives gain (loss) included in earnings   0 0 0
Securities gains (losses) | MSRs        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Assets gain (loss) included in earnings   0 0 0
Securities gains (losses) | Municipal securities        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Assets gain (loss) included in earnings   0 0 1
Securities gains (losses) | Asset-backed securities        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Assets gain (loss) included in earnings   (2) (5) (2)
Securities gains (losses) | Automobile        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Assets gain (loss) included in earnings     0 0
Interest and fee income        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Net derivatives gain (loss) included in earnings   0 0  
Interest and fee income | MSRs        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Assets gain (loss) included in earnings   0 0  
Interest and fee income | Municipal securities        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Assets gain (loss) included in earnings   (3) (2)  
Interest and fee income | Asset-backed securities        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Assets gain (loss) included in earnings   $ 0 0  
Interest and fee income | Automobile        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Assets gain (loss) included in earnings     0  
Noninterest income        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Net derivatives gain (loss) included in earnings     0 0
Noninterest income | MSRs        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Assets gain (loss) included in earnings     0 0
Noninterest income | Municipal securities        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Assets gain (loss) included in earnings     0 6
Noninterest income | Asset-backed securities        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Assets gain (loss) included in earnings     0 0
Noninterest income | Automobile        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Assets gain (loss) included in earnings     $ 1 $ (2)