Quarterly report pursuant to Section 13 or 15(d)

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

v3.5.0.2
FAIR VALUES OF ASSETS AND LIABILITIES - Significant Unobservable Level 3 Inputs (Details) - USD ($)
$ in Thousands
 9 Months Ended 12 Months Ended
Sep. 30, 2016
Dec. 31, 2015
Fair Value Disclosures [Abstract]    
Available-for-sale and other securities $ 16,470,374 $ 8,775,441
Consumer loans 89,190 0
Fair Value, Measurements, Recurring    
Fair Value Disclosures [Abstract]    
MSRs 12,428 17,585
Available-for-sale and other securities 15,978,294 8,442,655
Fair Value, Measurements, Recurring | Level 3    
Fair Value Disclosures [Abstract]    
MSRs 12,428 17,585
Gross amounts of recognized assets 15,483 6,721
Gross amounts of recognized liabilities 6,883 665
Available-for-sale and other securities 2,979,092 2,195,888
Consumer loans 53,285 1,748
Fair Value, Measurements, Nonrecurring    
Fair Value Disclosures [Abstract]    
Impaired loans Fair Value Disclosure   62,029
Accrued income and other assets Fair Value Disclosure   27,342
Asset-backed Securities | Fair Value, Measurements, Recurring    
Fair Value Disclosures [Abstract]    
Available-for-sale and other securities 1,081,182 861,413
Asset-backed Securities | Fair Value, Measurements, Recurring | Level 3    
Fair Value Disclosures [Abstract]    
Available-for-sale and other securities 73,819 100,337
Municipal securities    
Fair Value Disclosures [Abstract]    
Available-for-sale and other securities 3,311,161 2,456,396
Municipal securities | Fair Value, Measurements, Recurring    
Fair Value Disclosures [Abstract]    
Available-for-sale and other securities 3,311,161 2,456,396
Municipal securities | Fair Value, Measurements, Recurring | Level 3    
Fair Value Disclosures [Abstract]    
Available-for-sale and other securities $ 2,905,273 $ 2,095,551
Cost Approach Valuation Technique | Maximum | MSRs | Level 3    
Fair Value Disclosures [Abstract]    
Constant prepayment rate 26.50% 25.70%
Spread over forward interest rate swap rates 0.092 0.092
Cost Approach Valuation Technique | Maximum | Private label CMO | Level 3    
Fair Value Disclosures [Abstract]    
Discount rate 10.60% 7.20%
Cumulative default 37.80% 50.00%
Loss given default 80.00% 80.00%
Cost Approach Valuation Technique | Maximum | Asset-backed Securities | Level 3    
Fair Value Disclosures [Abstract]    
Discount rate 11.90% 10.90%
Cumulative prepayment rate 73.00% 100.00%
Cumulative default 100.00% 100.00%
Loss given default 100.00% 100.00%
Cure given deferral 75.00% 75.00%
Cost Approach Valuation Technique | Maximum | Automobile | Level 3    
Fair Value Disclosures [Abstract]    
Discount rate 16.20% 5.00%
Cost Approach Valuation Technique | Minimum | MSRs | Level 3    
Fair Value Disclosures [Abstract]    
Constant prepayment rate 7.00% 7.90%
Spread over forward interest rate swap rates 0.030 0.033
Cost Approach Valuation Technique | Minimum | Private label CMO | Level 3    
Fair Value Disclosures [Abstract]    
Discount rate 0.00% 0.30%
Cumulative default 0.30% 0.10%
Loss given default 5.00% 5.00%
Cost Approach Valuation Technique | Minimum | Asset-backed Securities | Level 3    
Fair Value Disclosures [Abstract]    
Discount rate 4.90% 4.60%
Cumulative prepayment rate 0.00% 0.00%
Cumulative default 1.20% 1.60%
Loss given default 85.00% 85.00%
Cure given deferral 0.00% 0.00%
Cost Approach Valuation Technique | Minimum | Automobile | Level 3    
Fair Value Disclosures [Abstract]    
Discount rate 5.40% 0.20%
Cost Approach Valuation Technique | Weighted Average | MSRs | Level 3    
Fair Value Disclosures [Abstract]    
Constant prepayment rate 12.40% 14.70%
Spread over forward interest rate swap rates 0.055 0.054
Cost Approach Valuation Technique | Weighted Average | Private label CMO | Level 3    
Fair Value Disclosures [Abstract]    
Discount rate 3.60% 3.10%
Cumulative default 4.80% 2.10%
Loss given default 24.10% 20.50%
Cost Approach Valuation Technique | Weighted Average | Asset-backed Securities | Level 3    
Fair Value Disclosures [Abstract]    
Discount rate 6.20% 6.20%
Cumulative prepayment rate 7.80% 9.60%
Cumulative default 11.00% 11.10%
Loss given default 96.70% 96.60%
Cure given deferral 31.40% 36.80%
Cost Approach Valuation Technique | Weighted Average | Automobile | Level 3    
Fair Value Disclosures [Abstract]    
Constant prepayment rate   154.20%
Discount rate 5.60% 2.30%
Life of pool cumulative losses   2.10%
Market Approach Valuation Technique | Maximum | Derivative Instruments [Member] | Level 3    
Fair Value Disclosures [Abstract]    
Net market price 25.10% 20.90%
Estimated Pull through % 99.80% 99.80%
Market Approach Valuation Technique | Minimum | Derivative Instruments [Member] | Level 3    
Fair Value Disclosures [Abstract]    
Net market price (2.70%) (3.20%)
Estimated Pull through % 7.60% 11.90%
Market Approach Valuation Technique | Weighted Average | Derivative Instruments [Member] | Level 3    
Fair Value Disclosures [Abstract]    
Net market price 3.00% 1.90%
Estimated Pull through % 77.70% 76.70%