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
Jun. 30, 2017
Dec. 31, 2016
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]    
Amortized Cost $ 15,511,976 $ 15,776,855
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Available-for-sale and other securities 15,388,306 15,562,837
U.S. Treasury    
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]    
Amortized Cost, Under 1 year 10,139 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 10,641 5,480
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Fair Value, Under 1 year 10,139 4,988
Fair Value, 1-5 years 505 509
Fair Value, 6-10 years 0 0
Fair Value, Over 10 years 0 0
Available-for-sale and other securities 10,644 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 28,085 46,591
Amortized Cost, 6-10 years 200,334 173,941
Amortized Cost, Over 10 years 10,536,086 10,630,929
Amortized Cost 10,764,505 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 27,891 46,762
Fair Value, 6-10 years 199,224 176,404
Fair Value, Over 10 years 10,396,940 10,450,176
Available-for-sale and other securities 10,624,055 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 4,103 4,302
Amortized Cost, 1-5 years 9,498 5,092
Amortized Cost, 6-10 years 86,049 63,618
Amortized Cost, Over 10 years 0 0
Amortized Cost 99,650 73,012
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Fair Value, Under 1 year 4,142 4,367
Fair Value, 1-5 years 9,647 5,247
Fair Value, 6-10 years 86,502 63,928
Fair Value, Over 10 years 0 0
Available-for-sale and other securities 100,291 73,542
Total U.S. Treasury, Federal agency securities    
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]    
Amortized Cost 10,874,796 10,929,953
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Available-for-sale and other securities 10,734,990 10,752,381
Municipal securities    
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]    
Amortized Cost, Under 1 year 120,216 169,636
Amortized Cost, 1-5 years 1,113,974 933,893
Amortized Cost, 6-10 years 1,493,652 1,463,459
Amortized Cost, Over 10 years 555,096 693,440
Amortized Cost 3,282,938 3,260,428
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Fair Value, Under 1 year 121,345 166,887
Fair Value, 1-5 years 1,123,450 933,903
Fair Value, 6-10 years 1,508,930 1,464,583
Fair Value, Over 10 years 558,775 684,684
Available-for-sale and other securities 3,312,500 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 80,018 80,700
Amortized Cost, 6-10 years 144,969 223,352
Amortized Cost, Over 10 years 389,154 520,072
Amortized Cost 614,141 824,124
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Fair Value, Under 1 year 0 0
Fair Value, 1-5 years 80,177 80,560
Fair Value, 6-10 years 146,256 224,565
Fair Value, Over 10 years 368,366 488,356
Available-for-sale and other securities 594,799 793,481
Corporate debt    
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]    
Amortized Cost, Under 1 year 3,238 43,223
Amortized Cost, 1-5 years 64,369 78,430
Amortized Cost, 6-10 years 49,546 32,523
Amortized Cost, Over 10 years 21,386 40,361
Amortized Cost 138,539 194,537
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Fair Value, Under 1 year 3,268 43,603
Fair Value, 1-5 years 65,808 80,196
Fair Value, 6-10 years 51,878 32,865
Fair Value, Over 10 years 23,081 42,019
Available-for-sale and other securities 144,035 198,683
Other securities    
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]    
Amortized Cost, Under 1 year 3,151 1,650
Amortized Cost, 1-5 years 800 2,302
Amortized Cost, 6-10 years 0 0
Amortized Cost, Over 10 years 94 10
Amortized Cost 601,562 567,813
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Fair Value, Under 1 year 3,142 1,650
Fair Value, 1-5 years 790 2,283
Fair Value, 6-10 years 0 0
Fair Value, Over 10 years 94 10
Available-for-sale and other securities 601,982 568,235
Nonmarketable equity securities    
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]    
Amortized Cost 585,472 547,704
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Available-for-sale and other securities 585,471 547,704
Mutual funds    
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]    
Amortized Cost 11,184 15,286
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Available-for-sale and other securities 11,184 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