Securities (Details 4) (USD $)	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Securities available-for-sale:
Securities available-for-sale, Fair Value, Less than 12 months	$ 1,908,579,000	$ 1,940,958,000
Securities available-for-sale, Estimated Unrealized Loss, Less than 12 months	13,363,000	6,543,000
Securities available-for-sale, Fair Value, 12 months or greater	41,237,000	55,943,000
Securities available-for-sale, Estimated Unrealized Loss, 12 months or greater	6,128,000	8,001,000
Securities available-for-sale, Fair Value, Total	1,949,816,000	1,996,901,000
Securities available-for-sale, Estimated Unrealized Loss, Total	19,491,000	14,544,000
Securities held-to-maturity:
Securities held-to-maturity, Fair Value, Less than 12 months	333,776,000	156,856,000
Securities held-to-maturity, Estimated Unrealized Loss, Less than 12 months	5,477,000	1,421,000
Securities held-to-maturity, Fair Value, Total	333,776,000	156,856,000
Securities held-to-maturity, Estimated Unrealized Loss, Total	5,477,000	1,421,000
Other information
Fair value securities, having non-credit impairment recognized in AOCI	9,300,000	16,200,000
Temporarily impaired securities	1,940,000,000	1,980,000,000
Impairment losses recognized in earnings on other-than-temporarily impaired securities	0
U.S. Treasury
Securities available-for-sale:
Securities available-for-sale, Fair Value, Less than 12 months		5,096,000
Securities available-for-sale, Estimated Unrealized Loss, Less than 12 months		3,000
Securities available-for-sale, Fair Value, Total		5,096,000
Securities available-for-sale, Estimated Unrealized Loss, Total		3,000
Other information
Number of available-for-sale and held-to-maturity securities in the unrealized loss position		2
Federal agency - Debt
Securities available-for-sale:
Securities available-for-sale, Fair Value, Less than 12 months	141,151,000	346,136,000
Securities available-for-sale, Estimated Unrealized Loss, Less than 12 months	(73,000)	203,000
Securities available-for-sale, Fair Value, Total	141,151,000	346,136,000
Securities available-for-sale, Estimated Unrealized Loss, Total	(73,000)	203,000
Other information
Number of available-for-sale and held-to-maturity securities in the unrealized loss position	4	8
Federal agency - MBS
Securities available-for-sale:
Securities available-for-sale, Fair Value, Less than 12 months	84,678,000	50,932,000
Securities available-for-sale, Estimated Unrealized Loss, Less than 12 months	937,000	69,000
Securities available-for-sale, Fair Value, 12 months or greater	46,000	46,000
Securities available-for-sale, Fair Value, Total	84,724,000	50,978,000
Securities available-for-sale, Estimated Unrealized Loss, Total	937,000	69,000
Securities held-to-maturity:
Securities held-to-maturity, Fair Value, Less than 12 months	96,961,000	31,514,000
Securities held-to-maturity, Estimated Unrealized Loss, Less than 12 months	946,000	182,000
Securities held-to-maturity, Fair Value, Total	96,961,000	31,514,000
Securities held-to-maturity, Estimated Unrealized Loss, Total	946,000	182,000
Other information
Number of available-for-sale and held-to-maturity securities in the unrealized loss position	15	7
CMOs - Federal agency
Securities available-for-sale:
Securities available-for-sale, Fair Value, Less than 12 months	1,617,943,000	1,413,367,000
Securities available-for-sale, Estimated Unrealized Loss, Less than 12 months	11,395,000	5,994,000
Securities available-for-sale, Fair Value, 12 months or greater	3,301,000	13,565,000
Securities available-for-sale, Estimated Unrealized Loss, 12 months or greater	2,000	44,000
Securities available-for-sale, Fair Value, Total	1,621,244,000	1,426,932,000
Securities available-for-sale, Estimated Unrealized Loss, Total	11,397,000	6,038,000
Securities held-to-maturity:
Securities held-to-maturity, Fair Value, Less than 12 months	108,876,000	60,998,000
Securities held-to-maturity, Estimated Unrealized Loss, Less than 12 months	1,960,000	382,000
Securities held-to-maturity, Fair Value, Total	108,876,000	60,998,000
Securities held-to-maturity, Estimated Unrealized Loss, Total	1,960,000	382,000
Other information
Number of available-for-sale and held-to-maturity securities in the unrealized loss position	64	53
CMOs - Non-agency
Securities available-for-sale:
Securities available-for-sale, Fair Value, 12 months or greater	19,090,000	25,484,000
Securities available-for-sale, Estimated Unrealized Loss, 12 months or greater	889,000	2,124,000
Securities available-for-sale, Fair Value, Total	19,090,000	25,484,000
Securities available-for-sale, Estimated Unrealized Loss, Total	889,000	2,124,000
Other information
Number of available-for-sale and held-to-maturity securities in the unrealized loss position	3	4
State and municipal
Securities available-for-sale:
Securities available-for-sale, Fair Value, Less than 12 months	45,745,000	85,550,000
Securities available-for-sale, Estimated Unrealized Loss, Less than 12 months	950,000	225,000
Securities available-for-sale, Fair Value, 12 months or greater	3,530,000	810,000
Securities available-for-sale, Estimated Unrealized Loss, 12 months or greater	70,000	14,000
Securities available-for-sale, Fair Value, Total	49,275,000	86,360,000
Securities available-for-sale, Estimated Unrealized Loss, Total	1,020,000	239,000
Securities held-to-maturity:
Securities held-to-maturity, Fair Value, Less than 12 months	127,939,000	64,344,000
Securities held-to-maturity, Estimated Unrealized Loss, Less than 12 months	2,571,000	857,000
Securities held-to-maturity, Fair Value, Total	127,939,000	64,344,000
Securities held-to-maturity, Estimated Unrealized Loss, Total	2,571,000	857,000
Other information
Number of available-for-sale and held-to-maturity securities in the unrealized loss position	249	152
Other debt securities
Securities available-for-sale:
Securities available-for-sale, Fair Value, Less than 12 months	19,062,000	39,877,000
Securities available-for-sale, Estimated Unrealized Loss, Less than 12 months	8,000	49,000
Securities available-for-sale, Fair Value, 12 months or greater	15,270,000	16,038,000
Securities available-for-sale, Estimated Unrealized Loss, 12 months or greater	5,167,000	5,819,000
Securities available-for-sale, Fair Value, Total	34,332,000	55,915,000
Securities available-for-sale, Estimated Unrealized Loss, Total	5,175,000	5,868,000
Securities held-to-maturity:
Number of highly rated corporate debt and collateralized bond obligations	2
Other information
Number of available-for-sale and held-to-maturity securities in the unrealized loss position	2	5
Total debt securities
Other information
Number of available-for-sale and held-to-maturity securities in the unrealized loss position	337	231
Collateralized debt obligations
Securities available-for-sale:
Securities available-for-sale, Fair Value, Total	$ 5,200,000
Securities held-to-maturity:
Number of CDO's on which substantial paydown was received	1