Quarterly report pursuant to Section 13 or 15(d)

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

v3.8.0.1
FAIR VALUES OF ASSETS AND LIABILITIES - Significant Unobservable Level 3 Inputs (Details) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2018
Dec. 31, 2017
Fair Value Disclosures [Abstract]    
Gross amounts of recognized assets $ 356,000 $ 322,000
Derivative Liability, Fair Value, Gross Liability 439,000 331,000
Available-for-sale securities 14,607,000 14,869,000
Consumer loans 86,000 93,000
Fair Value, Measurements, Recurring    
Fair Value Disclosures [Abstract]    
MSRs 12,000 11,000
Available-for-sale securities 14,607,000 14,869,000
Fair Value, Measurements, Recurring | Level 3    
Fair Value Disclosures [Abstract]    
MSRs 12,000 11,000
Gross amounts of recognized assets 6,000 6,000
Derivative Liability, Fair Value, Gross Liability 6,000 5,000
Available-for-sale securities 3,230,000 3,191,000
Consumer loans 37,000 38,000
Fair Value, Measurements, Nonrecurring    
Fair Value Disclosures [Abstract]    
Impaired loans Fair Value Disclosure   36,000
Accrued income and other assets Fair Value Disclosure   33,000
Fair Value, Measurements, Nonrecurring | Level 3    
Fair Value Disclosures [Abstract]    
MSRs   190,000
Asset-backed securities    
Fair Value Disclosures [Abstract]    
Available-for-sale securities 427,000 467,000
Asset-backed securities | Fair Value, Measurements, Recurring    
Fair Value Disclosures [Abstract]    
Available-for-sale securities 427,000 467,000
Asset-backed securities | Fair Value, Measurements, Recurring | Level 3    
Fair Value Disclosures [Abstract]    
Available-for-sale securities 0 24,000
Municipal securities    
Fair Value Disclosures [Abstract]    
Available-for-sale securities 3,834,000 3,878,000
Municipal securities | Fair Value, Measurements, Recurring    
Fair Value Disclosures [Abstract]    
Available-for-sale securities 3,834,000 3,878,000
Municipal securities | Fair Value, Measurements, Recurring | Level 3    
Fair Value Disclosures [Abstract]    
Available-for-sale securities $ 3,230,000 $ 3,167,000
Cost Approach Valuation Technique | Maximum | Fair Value, Measurements, Recurring | MSRs | Level 3    
Fair Value Disclosures [Abstract]    
Constant prepayment rate 31.00% 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 9.00% 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 22.00% 22.00%
Discount rate 18.00% 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 0.00% 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 2.00% 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 9.00% 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 3.00% 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 8.00% 9.00%
Discount rate 8.00% 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 [Member] | Level 3    
Fair Value Disclosures [Abstract]    
Net market price 20.00% 20.00%
Estimated Pull through % 100.00% 100.00%
Market Approach Valuation Technique | Minimum | Fair Value, Measurements, Recurring | Derivative [Member] | Level 3    
Fair Value Disclosures [Abstract]    
Net market price (5.00%) (5.00%)
Estimated Pull through % 0.00% 3.00%
Market Approach Valuation Technique | Weighted Average | Fair Value, Measurements, Recurring | Derivative [Member] | Level 3    
Fair Value Disclosures [Abstract]    
Net market price 2.00% 2.00%
Estimated Pull through % 85.00% 75.00%
Derivative Financial Instruments, Liabilities [Member] | Market Approach Valuation Technique | Minimum | Level 3    
Fair Value Disclosures [Abstract]    
Fair Value Inputs, Estimated conversion factor 165.00% 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 Mar. 31, 2018 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 Jun. 30, 2020