Quarterly report pursuant to Section 13 or 15(d)

AVAILABLE-FOR-SALE AND OTHER SECURITIES - Schedule of Amortized Cost, Fair Value, and Gross Unrealized Gains and Losses (Details)

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AVAILABLE-FOR-SALE AND OTHER SECURITIES - Schedule of Amortized Cost, Fair Value, and Gross Unrealized Gains and Losses (Details) - USD ($)
$ in Thousands
Sep. 30, 2016
Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost $ 16,391,679 $ 8,770,923
Unrealized Gross Gains 155,891 88,169
Unrealized Gross Losses (77,196) (83,651)
Fair Value 16,470,374 8,775,441
U.S. Treasury    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 6,474 5,457
Unrealized Gross Gains 35 15
Unrealized Gross Losses 0 0
Fair Value 6,509 5,472
Federal agencies: Mortgage-backed securities    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 10,809,032 4,505,318
Unrealized Gross Gains 79,940 30,078
Unrealized Gross Losses (8,092) (13,708)
Fair Value 10,880,880 4,521,688
Federal agencies, Other agencies    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 123,218 115,076
Unrealized Gross Gains 2,553 888
Unrealized Gross Losses 0 (51)
Fair Value 125,771 115,913
Total U.S. Treasury, Federal agency securities    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 10,938,724 4,625,851
Unrealized Gross Gains 82,528 30,981
Unrealized Gross Losses (8,092) (13,759)
Fair Value 11,013,160 4,643,073
Municipal securities    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 3,294,173 2,431,943
Unrealized Gross Gains 54,452 51,558
Unrealized Gross Losses (37,464) (27,105)
Fair Value 3,311,161 2,456,396
Asset-backed securities    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 1,106,875 901,059
Unrealized Gross Gains 5,633 535
Unrealized Gross Losses (31,326) (40,181)
Fair Value 1,081,182 861,413
Corporate debt    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 539,964 464,207
Unrealized Gross Gains 12,838 4,824
Unrealized Gross Losses (311) (2,554)
Fair Value 552,491 466,477
Other securities    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 511,943 347,863
Unrealized Gross Gains 440 271
Unrealized Gross Losses (3) (52)
Fair Value $ 512,380 $ 348,082