Quarterly report pursuant to Section 13 or 15(d)

HELD-TO-MATURITY SECURITIES - Amortized Cost, Gross Unrealized Gains and Losses, & Fair Value (Details)

v3.5.0.2
HELD-TO-MATURITY SECURITIES - Amortized Cost, Gross Unrealized Gains and Losses, & Fair Value (Details) - USD ($)
$ in Thousands
Jun. 30, 2016
Dec. 31, 2015
Schedule of Held-to-maturity Securities [Line Items]    
Amortized Cost $ 5,658,565 $ 6,159,590
Unrealized Gross Gains 129,706 16,282
Unrealized Gross Losses (2,047) (40,414)
Fair Value 5,786,224 6,135,458
Federal agencies: Mortgage-backed securities    
Schedule of Held-to-maturity Securities [Line Items]    
Amortized Cost 5,059,077 5,532,501
Unrealized Gross Gains 114,311 14,637
Unrealized Gross Losses (2,047) (37,504)
Fair Value 5,171,341 5,509,634
Federal agencies, Other agencies    
Schedule of Held-to-maturity Securities [Line Items]    
Amortized Cost 592,863 620,052
Unrealized Gross Gains 15,267 1,645
Unrealized Gross Losses 0 (2,786)
Fair Value 608,130 618,911
Total U.S. Treasury, Federal agency securities    
Schedule of Held-to-maturity Securities [Line Items]    
Amortized Cost 5,651,940 6,152,553
Unrealized Gross Gains 129,578 16,282
Unrealized Gross Losses (2,047) (40,290)
Fair Value 5,779,471 6,128,545
Municipal securities    
Schedule of Held-to-maturity Securities [Line Items]    
Amortized Cost 6,625 7,037
Unrealized Gross Gains 128 0
Unrealized Gross Losses 0 (124)
Fair Value $ 6,753 $ 6,913