Securities (Details 4) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Securities available-for-sale:
Securities available-for-sale, Fair Value, Less than 12 months	$ 739,038	$ 2,708,675
Securities available-for-sale, Estimated Unrealized Loss, Less than 12 months	2,014	44,276
Securities available-for-sale, Fair Value, 12 months or greater	1,673,111	784,342
Securities available-for-sale, Estimated Unrealized Loss, 12 months or greater	43,159	38,365
Securities available-for-sale, Fair Value, Total	2,412,149	3,493,017
Securities available-for-sale, Estimated Unrealized Loss, Total	45,173	82,641
Securities held-to-maturity:
Securities held-to-maturity, Fair Value, Less than 12 months	717,719	2,462,226
Securities held-to-maturity, Estimated Unrealized Loss, Less than 12 months	8,775	66,879
Securities held-to-maturity, Fair Value, 12 months or greater	702,863	119,716
Securities held-to-maturity, Estimated Unrealized Loss, 12 months or greater	17,626	10,427
Securities held-to-maturity, Fair Value, Total	1,420,582	2,581,942
Securities held-to-maturity, Estimated Unrealized Loss, Total	26,401	77,306
Federal agency - Debt
Securities available-for-sale:
Securities available-for-sale, Fair Value, Less than 12 months	104,163	1,026,142
Securities available-for-sale, Estimated Unrealized Loss, Less than 12 months	31	7,911
Securities available-for-sale, Fair Value, 12 months or greater	312,696
Securities available-for-sale, Estimated Unrealized Loss, 12 months or greater	1,460
Securities available-for-sale, Fair Value, Total	416,859	1,026,142
Securities available-for-sale, Estimated Unrealized Loss, Total	1,491	7,911
Securities held-to-maturity:
Securities held-to-maturity, Fair Value, Less than 12 months		156,290
Securities held-to-maturity, Estimated Unrealized Loss, Less than 12 months		5,122
Securities held-to-maturity, Fair Value, 12 months or greater	76,094
Securities held-to-maturity, Estimated Unrealized Loss, 12 months or greater	856
Securities held-to-maturity, Fair Value, Total	76,094	156,290
Securities held-to-maturity, Estimated Unrealized Loss, Total	856	5,122
Other information
Number of available-for-sale and held-to-maturity securities in the unrealized loss position	22	47
Federal agency - MBS
Securities available-for-sale:
Securities available-for-sale, Fair Value, Less than 12 months	17,834	17,962
Securities available-for-sale, Estimated Unrealized Loss, Less than 12 months	70	85
Securities available-for-sale, Fair Value, 12 months or greater	42,442	43,492
Securities available-for-sale, Estimated Unrealized Loss, 12 months or greater	1,507	2,703
Securities available-for-sale, Fair Value, Total	60,276	61,454
Securities available-for-sale, Estimated Unrealized Loss, Total	1,577	2,788
Securities held-to-maturity:
Securities held-to-maturity, Fair Value, Less than 12 months	27,802	321,090
Securities held-to-maturity, Estimated Unrealized Loss, Less than 12 months	154	10,513
Securities held-to-maturity, Fair Value, 12 months or greater	123,966	15,338
Securities held-to-maturity, Estimated Unrealized Loss, 12 months or greater	3,904	1,417
Securities held-to-maturity, Fair Value, Total	151,768	336,428
Securities held-to-maturity, Estimated Unrealized Loss, Total	4,058	11,930
Other information
Number of available-for-sale and held-to-maturity securities in the unrealized loss position	29	44
CMOs - Federal agency
Securities available-for-sale:
Securities available-for-sale, Fair Value, Less than 12 months	615,321	1,637,994
Securities available-for-sale, Estimated Unrealized Loss, Less than 12 months	1,909	35,922
Securities available-for-sale, Fair Value, 12 months or greater	1,299,169	728,101
Securities available-for-sale, Estimated Unrealized Loss, 12 months or greater	39,695	34,849
Securities available-for-sale, Fair Value, Total	1,914,490	2,366,095
Securities available-for-sale, Estimated Unrealized Loss, Total	41,604	70,771
Securities held-to-maturity:
Securities held-to-maturity, Fair Value, Less than 12 months	619,017	1,539,464
Securities held-to-maturity, Estimated Unrealized Loss, Less than 12 months	8,334	36,435
Securities held-to-maturity, Fair Value, 12 months or greater	362,367	63,276
Securities held-to-maturity, Estimated Unrealized Loss, 12 months or greater	8,200	4,186
Securities held-to-maturity, Fair Value, Total	981,384	1,602,740
Securities held-to-maturity, Estimated Unrealized Loss, Total	16,534	40,621
Other information
Number of available-for-sale and held-to-maturity securities in the unrealized loss position	140	182
CMOs - Non-agency
Securities available-for-sale:
Securities available-for-sale, Fair Value, Less than 12 months		10,056
Securities available-for-sale, Estimated Unrealized Loss, Less than 12 months		319
Securities available-for-sale, Fair Value, 12 months or greater	13,610	8,483
Securities available-for-sale, Estimated Unrealized Loss, 12 months or greater	400	729
Securities available-for-sale, Fair Value, Total	13,610	18,539
Securities available-for-sale, Estimated Unrealized Loss, Total	400	1,048
Other information
Number of available-for-sale and held-to-maturity securities in the unrealized loss position	2	4
State and municipal
Securities available-for-sale:
Securities available-for-sale, Fair Value, Less than 12 months	1,720	16,521
Securities available-for-sale, Estimated Unrealized Loss, Less than 12 months	4	39
Securities available-for-sale, Fair Value, 12 months or greater	5,194	4,266
Securities available-for-sale, Estimated Unrealized Loss, 12 months or greater	97	84
Securities available-for-sale, Fair Value, Total	6,914	20,787
Securities available-for-sale, Estimated Unrealized Loss, Total	101	123
Securities held-to-maturity:
Securities held-to-maturity, Fair Value, Less than 12 months	46,463	347,305
Securities held-to-maturity, Estimated Unrealized Loss, Less than 12 months	283	14,190
Securities held-to-maturity, Fair Value, 12 months or greater	140,436	41,102
Securities held-to-maturity, Estimated Unrealized Loss, 12 months or greater	4,666	4,824
Securities held-to-maturity, Fair Value, Total	186,899	388,407
Securities held-to-maturity, Estimated Unrealized Loss, Total	4,949	19,014
Other information
Number of available-for-sale and held-to-maturity securities in the unrealized loss position	325	520
Other debt securities
Securities held-to-maturity:
Securities held-to-maturity, Fair Value, Less than 12 months	24,437	98,077
Securities held-to-maturity, Estimated Unrealized Loss, Less than 12 months	4	619
Securities held-to-maturity, Fair Value, Total	24,437	98,077
Securities held-to-maturity, Estimated Unrealized Loss, Total	$ 4	$ 619
Other information
Number of available-for-sale and held-to-maturity securities in the unrealized loss position	2	12
Total debt securities
Other information
Number of available-for-sale and held-to-maturity securities in the unrealized loss position	520	809