Quarterly report pursuant to Section 13 or 15(d)

AVAILABLE-FOR-SALE AND OTHER SECURITIES - Contractual Maturities (Details)

v3.7.0.1
AVAILABLE-FOR-SALE AND OTHER SECURITIES - Contractual Maturities (Details) - USD ($)
$ in Thousands
Mar. 31, 2017
Dec. 31, 2016
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]    
Amortized Cost $ 16,375,549 $ 15,776,855
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Available-for-sale and other securities 16,173,605 15,562,837
U.S. Treasury    
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]    
Amortized Cost, Under 1 year 6,379 4,978
Amortized Cost, 1-5 years 502 502
Amortized Cost, 6-10 years 0 0
Amortized Cost, Over 10 years 0 0
Amortized Cost 6,881 5,480
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Fair Value, Under 1 year 6,383 4,988
Fair Value, 1-5 years 507 509
Fair Value, 6-10 years 0 0
Fair Value, Over 10 years 0 0
Available-for-sale and other securities 6,890 5,497
Federal agencies: Mortgage-backed securities    
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]    
Amortized Cost, Under 1 year 0 0
Amortized Cost, 1-5 years 41,925 46,591
Amortized Cost, 6-10 years 273,555 173,941
Amortized Cost, Over 10 years 11,099,533 10,630,929
Amortized Cost 11,415,013 10,851,461
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Fair Value, Under 1 year 0 0
Fair Value, 1-5 years 41,995 46,762
Fair Value, 6-10 years 274,738 176,404
Fair Value, Over 10 years 10,905,134 10,450,176
Available-for-sale and other securities 11,221,867 10,673,342
Federal agencies, Other agencies    
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]    
Amortized Cost, Under 1 year 4,354 4,302
Amortized Cost, 1-5 years 9,503 5,092
Amortized Cost, 6-10 years 75,673 63,618
Amortized Cost, Over 10 years 0 0
Amortized Cost 89,530 73,012
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Fair Value, Under 1 year 4,417 4,367
Fair Value, 1-5 years 9,690 5,247
Fair Value, 6-10 years 75,736 63,928
Fair Value, Over 10 years 0 0
Available-for-sale and other securities 89,843 73,542
Total U.S. Treasury, Federal agency securities    
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]    
Amortized Cost 11,511,424 10,929,953
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Available-for-sale and other securities 11,318,600 10,752,381
Municipal securities    
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]    
Amortized Cost, Under 1 year 180,536 169,636
Amortized Cost, 1-5 years 951,261 933,893
Amortized Cost, 6-10 years 1,481,804 1,463,459
Amortized Cost, Over 10 years 689,993 693,440
Amortized Cost 3,303,594 3,260,428
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Fair Value, Under 1 year 178,416 166,887
Fair Value, 1-5 years 953,776 933,903
Fair Value, 6-10 years 1,493,797 1,464,583
Fair Value, Over 10 years 691,165 684,684
Available-for-sale and other securities 3,317,154 3,250,057
Asset-backed securities    
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]    
Amortized Cost, Under 1 year 0 0
Amortized Cost, 1-5 years 88,216 80,700
Amortized Cost, 6-10 years 168,634 223,352
Amortized Cost, Over 10 years 537,534 520,072
Amortized Cost 794,384 824,124
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Fair Value, Under 1 year 0 0
Fair Value, 1-5 years 88,681 80,560
Fair Value, 6-10 years 170,102 224,565
Fair Value, Over 10 years 508,154 488,356
Available-for-sale and other securities 766,937 793,481
Corporate debt    
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]    
Amortized Cost, Under 1 year 59,021 43,223
Amortized Cost, 1-5 years 64,529 78,430
Amortized Cost, 6-10 years 34,681 32,523
Amortized Cost, Over 10 years 36,098 40,361
Amortized Cost 194,329 194,537
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Fair Value, Under 1 year 59,429 43,603
Fair Value, 1-5 years 66,027 80,196
Fair Value, 6-10 years 35,362 32,865
Fair Value, Over 10 years 37,863 42,019
Available-for-sale and other securities 198,681 198,683
Other securities    
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]    
Amortized Cost, Under 1 year 1,652 1,650
Amortized Cost, 1-5 years 2,300 2,302
Amortized Cost, 6-10 years 0 0
Amortized Cost, Over 10 years 46 10
Amortized Cost 571,818 567,813
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Fair Value, Under 1 year 1,652 1,650
Fair Value, 1-5 years 2,275 2,283
Fair Value, 6-10 years 0 0
Fair Value, Over 10 years 46 10
Available-for-sale and other securities 572,233 568,235
Nonmarketable equity securities    
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]    
Amortized Cost 552,628 547,704
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Available-for-sale and other securities 552,628 547,704
Mutual funds    
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]    
Amortized Cost 14,331 15,286
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Available-for-sale and other securities 14,331 15,286
Marketable equity securities    
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]    
Amortized Cost 861 861
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Available-for-sale and other securities $ 1,301 $ 1,302