Quarterly report pursuant to Section 13 or 15(d)

FAIR VALUES OF ASSETS AND LIABILITIES - Level 3 Roll Forward (Details)

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FAIR VALUES OF ASSETS AND LIABILITIES - Level 3 Roll Forward (Details) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Dec. 31, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Available-for-sale securities $ 14,607,000   $ 14,869,000
MSRs      
Assets Level 3 Roll Forward:      
Opening balance 11,000 $ 14,000  
Transfers into Level 3 0 0  
Transfers out of Level 3 (1) 0 0  
Total gains/losses for the period:      
Included in earnings 1,000 (1,000)  
Included in OCI 0 0  
Purchases/originations 0 0  
Sales 0 0  
Repayments 0 0  
Settlements 0 0  
Closing balance 12,000 13,000  
Change in unrealized gains or losses for the period included in earnings for assets held at end of the reporting date 1,000 0  
Derivative [Member]      
Assets Level 3 Roll Forward:      
Opening balance (1,000) (2,000)  
Transfers into Level 3 0 0  
Transfers out of Level 3 (1) 5,000 0  
Total gains/losses for the period:      
Included in earnings 6,000 5,000  
Included in OCI 0 0  
Purchases/originations 0 0  
Sales 0 0  
Repayments 0 0  
Settlements 0 0  
Closing balance 0 3,000  
Change in unrealized gains or losses for the period included in earnings for assets held at end of the reporting date 0 5,000  
Municipal securities      
Assets Level 3 Roll Forward:      
Opening balance 3,167,000 2,798,000  
Transfers into Level 3 0 0  
Transfers out of Level 3 (1) 0 0  
Total gains/losses for the period:      
Included in earnings (1,000) (1,000)  
Included in OCI (28,000) 20,000  
Purchases/originations 193,000 133,000  
Sales 0  
Repayments 0 0  
Settlements (101,000) (82,000)  
Closing balance 3,230,000 2,868,000  
Change in unrealized gains or losses for the period included in earnings for assets held at end of the reporting date 0 20,000  
Asset-backed securities      
Assets Level 3 Roll Forward:      
Opening balance 24,000 76,000  
Transfers into Level 3 0 0  
Transfers out of Level 3 (1) 0 0  
Total gains/losses for the period:      
Included in earnings (2,000) 0  
Included in OCI 11,000 3,000  
Purchases/originations 0 0  
Sales (33,000) (19,000)  
Repayments 0 0  
Settlements 0 (1,000)  
Closing balance 0 59,000  
Change in unrealized gains or losses for the period included in earnings for assets held at end of the reporting date 0 1,000  
Automobile      
Assets Level 3 Roll Forward:      
Opening balance 38,000 48,000  
Transfers into Level 3 0 0  
Transfers out of Level 3 (1) 0 0  
Total gains/losses for the period:      
Included in earnings 0 0  
Included in OCI 0 0  
Purchases/originations 0 0  
Sales 0 0  
Repayments (1,000) (4,000)  
Settlements 0 0  
Closing balance 37,000 44,000  
Change in unrealized gains or losses for the period included in earnings for assets held at end of the reporting date 0 $ 0  
Commercial Mortgage Backed Securities [Member]      
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Available-for-sale securities 1,791,000   2,487,000
Residential Mortgage Backed Securities [Member]      
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Available-for-sale securities 724,000   1,367,000
Fair Value, Measurements, Recurring [Member]      
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Available-for-sale securities 14,607,000   14,869,000
Fair Value, Measurements, Recurring [Member] | Commercial Mortgage Backed Securities [Member]      
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Available-for-sale securities 1,791,000   2,487,000
Fair Value, Measurements, Recurring [Member] | Residential Mortgage Backed Securities [Member]      
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Available-for-sale securities 724,000   1,367,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Available-for-sale securities 11,372,000   11,673,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Commercial Mortgage Backed Securities [Member]      
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Available-for-sale securities 1,791,000   2,487,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Residential Mortgage Backed Securities [Member]      
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Available-for-sale securities $ 724,000   $ 1,367,000