Securities (Details 4) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Securities available-for-sale:
Securities available-for-sale, Fair Value, Less than 12 months	$ 1,940,958,000	$ 1,278,941,000
Securities available-for-sale, Estimated Unrealized Loss, Less than 12 months	6,543,000	4,221,000
Securities available-for-sale, Fair Value, 12 months or greater	55,943,000	48,141,000
Securities available-for-sale, Estimated Unrealized Loss, 12 months or greater	8,001,000	18,957,000
Securities available-for-sale, Fair Value, Total	1,996,901,000	1,327,082,000
Securities available-for-sale, Estimated Unrealized Loss, Total	14,544,000	23,178,000
Securities held-to-maturity:
Securities held-to-maturity, Fair Value, Less than 12 months	156,856,000	38,040,000
Securities held-to-maturity, Estimated Unrealized Loss, Less than 12 months	1,421,000	232,000
Securities held-to-maturity, Fair Value, Total	156,856,000	38,040,000
Securities held-to-maturity, Estimated Unrealized Loss, Total	1,421,000	232,000
Other information
Fair value securities, having non-credit impairment recognized in AOCI	16,200,000	9,200,000
Temporarily impaired securities	1,980,000,000	1,320,000,000
Impairment losses recognized in earnings on other-than-temporarily impaired securities	291,000	651,000	2,031,000
U.S. Treasury
Securities available-for-sale:
Securities available-for-sale, Fair Value, Less than 12 months	5,096,000	4,145,000
Securities available-for-sale, Estimated Unrealized Loss, Less than 12 months	3,000	5,000
Securities available-for-sale, Fair Value, Total	5,096,000	4,145,000
Securities available-for-sale, Estimated Unrealized Loss, Total	3,000	5,000
Other information
Number of available-for-sale and held-to-maturity securities in the unrealized loss position	2	2
Federal agency - Debt
Securities available-for-sale:
Securities available-for-sale, Fair Value, Less than 12 months	346,136,000	409,129,000
Securities available-for-sale, Estimated Unrealized Loss, Less than 12 months	203,000	296,000
Securities available-for-sale, Fair Value, Total	346,136,000	409,129,000
Securities available-for-sale, Estimated Unrealized Loss, Total	203,000	296,000
Other information
Number of available-for-sale and held-to-maturity securities in the unrealized loss position	8	12
Federal agency - MBS
Securities available-for-sale:
Securities available-for-sale, Fair Value, Less than 12 months	50,932,000	24,519,000
Securities available-for-sale, Estimated Unrealized Loss, Less than 12 months	69,000	87,000
Securities available-for-sale, Fair Value, 12 months or greater	46,000
Securities available-for-sale, Fair Value, Total	50,978,000	24,519,000
Securities available-for-sale, Estimated Unrealized Loss, Total	69,000	87,000
Securities held-to-maturity:
Securities held-to-maturity, Fair Value, Less than 12 months	31,514,000
Securities held-to-maturity, Estimated Unrealized Loss, Less than 12 months	182,000
Securities held-to-maturity, Fair Value, Total	31,514,000
Securities held-to-maturity, Estimated Unrealized Loss, Total	182,000
Other information
Number of available-for-sale and held-to-maturity securities in the unrealized loss position	7	3
CMOs - Federal agency
Securities available-for-sale:
Securities available-for-sale, Fair Value, Less than 12 months	1,413,367,000	744,737,000
Securities available-for-sale, Estimated Unrealized Loss, Less than 12 months	5,994,000	2,224,000
Securities available-for-sale, Fair Value, 12 months or greater	13,565,000
Securities available-for-sale, Estimated Unrealized Loss, 12 months or greater	44,000
Securities available-for-sale, Fair Value, Total	1,426,932,000	744,737,000
Securities available-for-sale, Estimated Unrealized Loss, Total	6,038,000	2,224,000
Securities held-to-maturity:
Securities held-to-maturity, Fair Value, Less than 12 months	60,998,000	32,256,000
Securities held-to-maturity, Estimated Unrealized Loss, Less than 12 months	382,000	195,000
Securities held-to-maturity, Fair Value, Total	60,998,000	32,256,000
Securities held-to-maturity, Estimated Unrealized Loss, Total	382,000	195,000
Other information
Number of available-for-sale and held-to-maturity securities in the unrealized loss position	53	36
CMOs - Non-agency
Securities available-for-sale:
Securities available-for-sale, Fair Value, Less than 12 months		20,094,000
Securities available-for-sale, Estimated Unrealized Loss, Less than 12 months		833,000
Securities available-for-sale, Fair Value, 12 months or greater	25,484,000	31,400,000
Securities available-for-sale, Estimated Unrealized Loss, 12 months or greater	2,124,000	10,487,000
Securities available-for-sale, Fair Value, Total	25,484,000	51,494,000
Securities available-for-sale, Estimated Unrealized Loss, Total	2,124,000	11,320,000
Other information
Number of available-for-sale and held-to-maturity securities in the unrealized loss position	4	12
Impairment losses recognized in earnings on other-than-temporarily impaired securities	291,000	651,000	1,738,000
State and municipal
Securities available-for-sale:
Securities available-for-sale, Fair Value, Less than 12 months	85,550,000	42,164,000
Securities available-for-sale, Estimated Unrealized Loss, Less than 12 months	225,000	268,000
Securities available-for-sale, Fair Value, 12 months or greater	810,000	2,023,000
Securities available-for-sale, Estimated Unrealized Loss, 12 months or greater	14,000	105,000
Securities available-for-sale, Fair Value, Total	86,360,000	44,187,000
Securities available-for-sale, Estimated Unrealized Loss, Total	239,000	373,000
Securities held-to-maturity:
Securities held-to-maturity, Fair Value, Less than 12 months	64,344,000	5,784,000
Securities held-to-maturity, Estimated Unrealized Loss, Less than 12 months	857,000	37,000
Securities held-to-maturity, Fair Value, Total	64,344,000	5,784,000
Securities held-to-maturity, Estimated Unrealized Loss, Total	857,000	37,000
Other information
Number of available-for-sale and held-to-maturity securities in the unrealized loss position	152	19
Other debt securities
Securities available-for-sale:
Securities available-for-sale, Fair Value, Less than 12 months	39,877,000	34,153,000
Securities available-for-sale, Estimated Unrealized Loss, Less than 12 months	49,000	508,000
Securities available-for-sale, Fair Value, 12 months or greater	16,038,000	14,718,000
Securities available-for-sale, Estimated Unrealized Loss, 12 months or greater	5,819,000	8,365,000
Securities available-for-sale, Fair Value, Total	55,915,000	48,871,000
Securities available-for-sale, Estimated Unrealized Loss, Total	$ 5,868,000	$ 8,873,000
Other information
Number of available-for-sale and held-to-maturity securities in the unrealized loss position	5	6
Total debt securities
Other information
Number of available-for-sale and held-to-maturity securities in the unrealized loss position	231	90