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
 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2016
Fair Value Disclosures [Abstract]      
Gross amounts of recognized assets $ 320,826   $ 420,159
Derivative Liability, Fair Value, Gross Liability 293,650   370,647
Available-for-sale and other securities 15,453,061   15,562,837
Consumer loans 99,191   82,319
Fair Value, Measurements, Recurring      
Fair Value Disclosures [Abstract]      
MSRs 11,753   13,747
Available-for-sale and other securities 14,870,042   15,015,133
Fair Value, Measurements, Recurring | Level 3      
Fair Value Disclosures [Abstract]      
MSRs 11,753   13,747
Gross amounts of recognized assets 8,425   5,747
Derivative Liability, Fair Value, Gross Liability 5,459   7,870
Available-for-sale and other securities 2,982,154   2,874,047
Consumer loans 40,483   47,880
Fair Value, Measurements, Nonrecurring      
Fair Value Disclosures [Abstract]      
Impaired loans Fair Value Disclosure     53,818
Accrued income and other assets Fair Value Disclosure     50,930
Fair Value, Measurements, Nonrecurring | Level 3      
Fair Value Disclosures [Abstract]      
MSRs     171,309
Asset-backed securities      
Fair Value Disclosures [Abstract]      
Available-for-sale and other securities 555,191   793,481
Asset-backed securities | Fair Value, Measurements, Recurring      
Fair Value Disclosures [Abstract]      
Available-for-sale and other securities 555,191   793,481
Asset-backed securities | Fair Value, Measurements, Recurring | Level 3      
Fair Value Disclosures [Abstract]      
Available-for-sale and other securities 24,127   76,003
Municipal securities      
Fair Value Disclosures [Abstract]      
Available-for-sale and other securities 3,426,109   3,250,057
Municipal securities | Fair Value, Measurements, Recurring      
Fair Value Disclosures [Abstract]      
Available-for-sale and other securities 3,426,109   3,250,057
Municipal securities | Fair Value, Measurements, Recurring | Level 3      
Fair Value Disclosures [Abstract]      
Available-for-sale and other securities $ 2,958,027   $ 2,798,044
Cost Approach Valuation Technique | Maximum | Fair Value, Measurements, Recurring | MSRs | Level 3      
Fair Value Disclosures [Abstract]      
Constant prepayment rate 31.00% 34.40%  
Spread over forward interest rate swap rates 0.1 0.092  
Cost Approach Valuation Technique | Maximum | Fair Value, Measurements, Recurring | Private label CMO | Level 3      
Fair Value Disclosures [Abstract]      
Discount rate 10.30% 10.00%  
Cumulative default 42.00% 37.80%  
Loss given default 80.00% 80.00%  
Cost Approach Valuation Technique | Maximum | Fair Value, Measurements, Recurring | Asset-backed securities | Level 3      
Fair Value Disclosures [Abstract]      
Constant prepayment rate 72.00% 73.00%  
Discount rate 6.80% 12.00%  
Cumulative default 100.00% 100.00%  
Loss given default 100.00% 100.00%  
Cure given deferral 100.00% 75.00%  
Cost Approach Valuation Technique | Maximum | Fair Value, Measurements, Recurring | Loans held for investment | Level 3      
Fair Value Disclosures [Abstract]      
Discount rate 17.70% 16.20%  
Cost Approach Valuation Technique | Maximum | Fair Value, Measurements, Nonrecurring | MSRs | Level 3      
Fair Value Disclosures [Abstract]      
Constant prepayment rate 21.00% 30.40%  
Spread over forward interest rate swap rates 0.2 0.2  
Cost Approach Valuation Technique | Minimum | Fair Value, Measurements, Recurring | MSRs | Level 3      
Fair Value Disclosures [Abstract]      
Constant prepayment rate 9.00% 5.63%  
Spread over forward interest rate swap rates 0.080 0.030  
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% 0.30%  
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 1.30% 5.00%  
Cumulative default 2.90% 1.10%  
Loss given default 90.00% 85.00%  
Cure given deferral 0.00% 0.00%  
Cost Approach Valuation Technique | Minimum | Fair Value, Measurements, Recurring | Loans held for investment | Level 3      
Fair Value Disclosures [Abstract]      
Discount rate 7.00% 5.40%  
Cost Approach Valuation Technique | Minimum | Fair Value, Measurements, Nonrecurring | MSRs | Level 3      
Fair Value Disclosures [Abstract]      
Constant prepayment rate 6.00% 5.57%  
Spread over forward interest rate swap rates 0.018 0.042  
Cost Approach Valuation Technique | Weighted Average | Fair Value, Measurements, Recurring | MSRs | Level 3      
Fair Value Disclosures [Abstract]      
Constant prepayment rate 12.00% 10.90%  
Spread over forward interest rate swap rates 0.081 0.054  
Cost Approach Valuation Technique | Weighted Average | Fair Value, Measurements, Recurring | Private label CMO | Level 3      
Fair Value Disclosures [Abstract]      
Discount rate 4.00% 3.60%  
Cumulative default 4.90% 4.00%  
Loss given default 23.70% 24.10%  
Cost Approach Valuation Technique | Weighted Average | Fair Value, Measurements, Recurring | Asset-backed securities | Level 3      
Fair Value Disclosures [Abstract]      
Constant prepayment rate 7.30% 6.50%  
Discount rate 6.50% 6.30%  
Cumulative default 8.60% 11.20%  
Loss given default 97.80% 96.30%  
Cure given deferral 0.00% 36.20%  
Cost Approach Valuation Technique | Weighted Average | Fair Value, Measurements, Recurring | Loans held for investment | Level 3      
Fair Value Disclosures [Abstract]      
Discount rate 8.20% 5.60%  
Cost Approach Valuation Technique | Weighted Average | Fair Value, Measurements, Nonrecurring | MSRs | Level 3      
Fair Value Disclosures [Abstract]      
Constant prepayment rate 8.00% 7.80%  
Spread over forward interest rate swap rates 0.104 0.117  
Market Approach Valuation Technique | Maximum | Fair Value, Measurements, Recurring | Derivative [Member] | Level 3      
Fair Value Disclosures [Abstract]      
Net market price 21.40% 25.40%  
Estimated Pull through % 99.00% 99.80%  
Market Approach Valuation Technique | Minimum | Fair Value, Measurements, Recurring | Derivative [Member] | Level 3      
Fair Value Disclosures [Abstract]      
Net market price (4.00%) (7.10%)  
Estimated Pull through % 11.00% 8.10%  
Market Approach Valuation Technique | Weighted Average | Fair Value, Measurements, Recurring | Derivative [Member] | Level 3      
Fair Value Disclosures [Abstract]      
Net market price 1.80% 1.10%  
Estimated Pull through % 79.00% 76.90%