Quarterly report pursuant to Section 13 or 15(d)

FAIR VALUES OF ASSETS AND LIABILITIES - Significant Unobservable Level 3 Inputs (Details)

v3.10.0.1
FAIR VALUES OF ASSETS AND LIABILITIES - Significant Unobservable Level 3 Inputs (Details) - USD ($)
$ in Millions
3 Months Ended 12 Months Ended
Sep. 30, 2018
Dec. 31, 2017
Fair Value Disclosures [Abstract]    
Gross amounts of recognized assets $ 498 $ 322
Derivative Liability, Fair Value, Gross Liability 441 331
Available-for-sale securities 13,727 14,869
Consumer loans 81 93
Fair Value, Measurements, Recurring    
Fair Value Disclosures [Abstract]    
MSRs 11 11
Available-for-sale securities 13,727 14,869
Fair Value, Measurements, Recurring | Level 3    
Fair Value Disclosures [Abstract]    
MSRs 11 11
Gross amounts of recognized assets 5 6
Derivative Liability, Fair Value, Gross Liability 4 5
Available-for-sale securities 3,277 3,191
Consumer loans 32 38
Fair Value, Measurements, Nonrecurring    
Fair Value Disclosures [Abstract]    
Impaired loans Fair Value Disclosure   36
Accrued income and other assets Fair Value Disclosure   33
Fair Value, Measurements, Nonrecurring | Level 3    
Fair Value Disclosures [Abstract]    
MSRs   190
Asset-backed securities    
Fair Value Disclosures [Abstract]    
Available-for-sale securities 363 467
Asset-backed securities | Fair Value, Measurements, Recurring    
Fair Value Disclosures [Abstract]    
Available-for-sale securities 363 467
Asset-backed securities | Fair Value, Measurements, Recurring | Level 3    
Fair Value Disclosures [Abstract]    
Available-for-sale securities 0 24
Municipal securities    
Fair Value Disclosures [Abstract]    
Available-for-sale securities 3,848 3,878
Municipal securities | Fair Value, Measurements, Recurring    
Fair Value Disclosures [Abstract]    
Available-for-sale securities 3,848 3,878
Municipal securities | Fair Value, Measurements, Recurring | Level 3    
Fair Value Disclosures [Abstract]    
Available-for-sale securities $ 3,277 $ 3,167
Cost Approach Valuation Technique | Maximum | Fair Value, Measurements, Recurring | MSRs | Level 3    
Fair Value Disclosures [Abstract]    
Constant prepayment rate 54.00% 33.00%
Spread over forward interest rate swap rates 0.11 0.10
Cost Approach Valuation Technique | Maximum | Fair Value, Measurements, Recurring | Private label CMO | Level 3    
Fair Value Disclosures [Abstract]    
Discount rate 4.00% 10.00%
Cumulative default 64.00% 64.00%
Loss given default 90.00% 90.00%
Cost Approach Valuation Technique | Maximum | Fair Value, Measurements, Recurring | Asset-backed securities | Level 3    
Fair Value Disclosures [Abstract]    
Constant prepayment rate 0.00% 72.00%
Discount rate 0.00% 7.00%
Cumulative default 0.00% 53.00%
Loss given default 0.00% 100.00%
Cure given deferral 0.00% 50.00%
Cost Approach Valuation Technique | Maximum | Fair Value, Measurements, Recurring | Loans held for investment | Level 3    
Fair Value Disclosures [Abstract]    
Constant prepayment rate 9.00% 22.00%
Discount rate 7.00% 18.00%
Cost Approach Valuation Technique | Maximum | Fair Value, Measurements, Nonrecurring | MSRs | Level 3    
Fair Value Disclosures [Abstract]    
Constant prepayment rate 0.00% 21.00%
Spread over forward interest rate swap rates 0 0.2
Cost Approach Valuation Technique | Minimum | Fair Value, Measurements, Recurring | MSRs | Level 3    
Fair Value Disclosures [Abstract]    
Constant prepayment rate 6.00% 8.00%
Spread over forward interest rate swap rates 0.05 0.08
Cost Approach Valuation Technique | Minimum | Fair Value, Measurements, Recurring | Private label CMO | Level 3    
Fair Value Disclosures [Abstract]    
Discount rate 3.00% 0.00%
Cumulative default 0.00% 0.00%
Loss given default 5.00% 5.00%
Cost Approach Valuation Technique | Minimum | Fair Value, Measurements, Recurring | Asset-backed securities | Level 3    
Fair Value Disclosures [Abstract]    
Constant prepayment rate 0.00% 0.00%
Discount rate 0.00% 7.00%
Cumulative default 0.00% 3.00%
Loss given default 0.00% 90.00%
Cure given deferral 0.00% 50.00%
Cost Approach Valuation Technique | Minimum | Fair Value, Measurements, Recurring | Loans held for investment | Level 3    
Fair Value Disclosures [Abstract]    
Constant prepayment rate 9.00% 2.00%
Discount rate 7.00% 7.00%
Cost Approach Valuation Technique | Minimum | Fair Value, Measurements, Nonrecurring | MSRs | Level 3    
Fair Value Disclosures [Abstract]    
Constant prepayment rate 0.00% 6.00%
Spread over forward interest rate swap rates 0 0.02
Cost Approach Valuation Technique | Weighted Average | Fair Value, Measurements, Recurring | MSRs | Level 3    
Fair Value Disclosures [Abstract]    
Constant prepayment rate 8.00% 12.00%
Spread over forward interest rate swap rates 0.080 0.080
Cost Approach Valuation Technique | Weighted Average | Fair Value, Measurements, Recurring | Private label CMO | Level 3    
Fair Value Disclosures [Abstract]    
Discount rate 3.00% 4.00%
Cumulative default 4.00% 3.00%
Loss given default 25.00% 24.00%
Cost Approach Valuation Technique | Weighted Average | Fair Value, Measurements, Recurring | Asset-backed securities | Level 3    
Fair Value Disclosures [Abstract]    
Constant prepayment rate 0.00% 7.00%
Discount rate 0.00% 7.00%
Cumulative default 0.00% 7.00%
Loss given default 0.00% 98.00%
Cure given deferral 0.00% 50.00%
Cost Approach Valuation Technique | Weighted Average | Fair Value, Measurements, Recurring | Loans held for investment | Level 3    
Fair Value Disclosures [Abstract]    
Constant prepayment rate 9.00% 9.00%
Discount rate 7.00% 8.00%
Cost Approach Valuation Technique | Weighted Average | Fair Value, Measurements, Nonrecurring | MSRs | Level 3    
Fair Value Disclosures [Abstract]    
Constant prepayment rate 0.00% 8.00%
Spread over forward interest rate swap rates 0.000 0.100
Market Approach Valuation Technique | Maximum | Fair Value, Measurements, Recurring | Derivative instruments | Level 3    
Fair Value Disclosures [Abstract]    
Net market price 8.00% 20.00%
Estimated Pull through % 100.00% 100.00%
Market Approach Valuation Technique | Minimum | Fair Value, Measurements, Recurring | Derivative instruments | Level 3    
Fair Value Disclosures [Abstract]    
Net market price (4.00%) (5.00%)
Estimated Pull through % 3.00% 3.00%
Market Approach Valuation Technique | Weighted Average | Fair Value, Measurements, Recurring | Derivative instruments | Level 3    
Fair Value Disclosures [Abstract]    
Net market price 2.00% 2.00%
Estimated Pull through % 90.00% 75.00%
Derivative Financial Instruments, Liabilities [Member] | Market Approach Valuation Technique | Level 3    
Fair Value Disclosures [Abstract]    
Fair Value Inputs, Timing of the resolution of the litigation Jun. 30, 2020  
Derivative Financial Instruments, Liabilities [Member] | Market Approach Valuation Technique | Minimum | Level 3    
Fair Value Disclosures [Abstract]    
Fair Value Inputs, Estimated conversion factor 163.00% 165.00%
Fair Value Inputs, Estimated growth rate of Visa Class A shares 7.00% 7.00%
Discount rate 3.00% 3.00%
Fair Value Inputs, Timing of the resolution of the litigation   Dec. 31, 2017
Derivative Financial Instruments, Liabilities [Member] | Market Approach Valuation Technique | Weighted Average | Level 3    
Fair Value Disclosures [Abstract]    
Fair Value Inputs, Timing of the resolution of the litigation   Jun. 30, 2020