Securities (Details 4) (USD $)	Sep. 30, 2012	Dec. 31, 2011
Securities available-for-sale:
Securities available-for-sale, Fair Value, Less than 12 months	$ 1,071,098,000	$ 1,278,941,000
Securities available-for-sale, Estimated Unrealized Loss, Less than 12 months	3,925,000	4,221,000
Securities available-for-sale, Fair Value, 12 months or greater	94,936,000	48,141,000
Securities available-for-sale, Estimated Unrealized Loss, 12 months or greater	9,641,000	18,957,000
Securities available-for-sale, Fair Value, Total	1,166,034,000	1,327,082,000
Securities available-for-sale, Estimated Unrealized Loss, Total	13,566,000	23,178,000
Securities held-to-maturity:
Securities held-to-maturity, Fair Value, Less than 12 months	20,274,000	38,040,000
Securities held-to-maturity, Estimated Unrealized Loss, Less than 12 months	152,000	232,000
Securities held-to-maturity, Fair Value, Total	20,274,000	38,040,000
Securities held-to-maturity, Estimated Unrealized Loss, Total	152,000	232,000
Other information
Fair value securities, having non-credit impairment recognized in AOCI	16,300,000	9,200,000
Temporarily impaired securities	1,150,000,000	1,320,000,000
U.S. Treasury
Securities available-for-sale:
Securities available-for-sale, Fair Value, Less than 12 months	5,108,000	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	5,108,000	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	90,220,000	409,129,000
Securities available-for-sale, Estimated Unrealized Loss, Less than 12 months	31,000	296,000
Securities available-for-sale, Fair Value, Total	90,220,000	409,129,000
Securities available-for-sale, Estimated Unrealized Loss, Total	31,000	296,000
Other information
Number of available-for-sale and held-to-maturity securities in the unrealized loss position	4	12
Federal agency - MBS
Securities available-for-sale:
Securities available-for-sale, Fair Value, Less than 12 months		24,519,000
Securities available-for-sale, Estimated Unrealized Loss, Less than 12 months		87,000
Securities available-for-sale, Fair Value, Total		24,519,000
Securities available-for-sale, Estimated Unrealized Loss, Total		87,000
Other information
Number of available-for-sale and held-to-maturity securities in the unrealized loss position		3
CMOs - Federal agency
Securities available-for-sale:
Securities available-for-sale, Fair Value, Less than 12 months	928,673,000	744,737,000
Securities available-for-sale, Estimated Unrealized Loss, Less than 12 months	3,763,000	2,224,000
Securities available-for-sale, Fair Value, 12 months or greater	49,923,000
Securities available-for-sale, Estimated Unrealized Loss, 12 months or greater	172,000
Securities available-for-sale, Fair Value, Total	978,596,000	744,737,000
Securities available-for-sale, Estimated Unrealized Loss, Total	3,935,000	2,224,000
Securities held-to-maturity:
Securities held-to-maturity, Fair Value, Less than 12 months		32,256,000
Securities held-to-maturity, Estimated Unrealized Loss, Less than 12 months		195,000
Securities held-to-maturity, Fair Value, Total		32,256,000
Securities held-to-maturity, Estimated Unrealized Loss, Total		195,000
Other information
Number of available-for-sale and held-to-maturity securities in the unrealized loss position	39	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	27,985,000	31,400,000
Securities available-for-sale, Estimated Unrealized Loss, 12 months or greater	3,012,000	10,487,000
Securities available-for-sale, Fair Value, Total	27,985,000	51,494,000
Securities available-for-sale, Estimated Unrealized Loss, Total	3,012,000	11,320,000
Other information
Number of available-for-sale and held-to-maturity securities in the unrealized loss position	5	12
State and municipal
Securities available-for-sale:
Securities available-for-sale, Fair Value, Less than 12 months	47,097,000	42,164,000
Securities available-for-sale, Estimated Unrealized Loss, Less than 12 months	128,000	268,000
Securities available-for-sale, Fair Value, 12 months or greater	808,000	2,023,000
Securities available-for-sale, Estimated Unrealized Loss, 12 months or greater	7,000	105,000
Securities available-for-sale, Fair Value, Total	47,905,000	44,187,000
Securities available-for-sale, Estimated Unrealized Loss, Total	135,000	373,000
Securities held-to-maturity:
Securities held-to-maturity, Fair Value, Less than 12 months	20,274,000	5,784,000
Securities held-to-maturity, Estimated Unrealized Loss, Less than 12 months	152,000	37,000
Securities held-to-maturity, Fair Value, Total	20,274,000	5,784,000
Securities held-to-maturity, Estimated Unrealized Loss, Total	152,000	37,000
Other information
Number of available-for-sale and held-to-maturity securities in the unrealized loss position	59	19
Other debt securities
Securities available-for-sale:
Securities available-for-sale, Fair Value, Less than 12 months		34,153,000
Securities available-for-sale, Estimated Unrealized Loss, Less than 12 months		508,000
Securities available-for-sale, Fair Value, 12 months or greater	16,220,000	14,718,000
Securities available-for-sale, Estimated Unrealized Loss, 12 months or greater	6,450,000	8,365,000
Securities available-for-sale, Fair Value, Total	16,220,000	48,871,000
Securities available-for-sale, Estimated Unrealized Loss, Total	6,450,000	8,873,000
Other information
Number of available-for-sale and held-to-maturity securities in the unrealized loss position	1	6
Collateralized debt obligations
Securities available-for-sale:
Securities available-for-sale, Estimated Unrealized Loss, Total	$ 6,400,000
Total debt securities
Other information
Number of available-for-sale and held-to-maturity securities in the unrealized loss position	110	90