Investment Securities Gross Unrealized Losses and Fair Values of Investments by Category and Length of Time in a Continuous Unrealized Loss Position (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011
Estimated Fair Value, less than 12 months, Available for Sale and Held To Maturity, Combined	$ 328,391
Unrealized Losses, less than 12 months, Available for Sale and Held to Maturity, Combined	(4,844)
Estimated Fair Value, 12 months or longer, Available for Sale and Held to Maturity, Combined	245,705
Unrealized Losses, 12 months or longer, Available for Sale and Held to Maturity, Combined	(29,522)
Estimated Fair Value, Total	574,096
Unrealized Losses, Total	(34,366)
U.S. Government-Sponsored Agency Securities [Member]
Estimated Fair Value, less than 12 months, Available for Sale and Held To Maturity, Combined	208
Unrealized Losses, less than 12 months, Available for Sale and Held to Maturity, Combined	(1)
Estimated Fair Value, 12 months or longer, Available for Sale and Held to Maturity, Combined	5,373
Unrealized Losses, 12 months or longer, Available for Sale and Held to Maturity, Combined	(14)
Estimated Fair Value, Total	5,581
Unrealized Losses, Total	(15)
Corporate Debt Securities [Member]
Estimated Fair Value, Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	14,256
Unrealized Losses, Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(757)
Estimated Fair Value, Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	41,704
Unrealized Losses, Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses,	(13,771)
Estimated Fair Value, Total	55,960
Unrealized Losses, Total	(14,528)
Collateralized Mortgage Obligations [Member]
Estimated Fair Value, Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	179,484
Unrealized Losses, Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(828)
Estimated Fair Value, Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0
Unrealized Losses, Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses,	0
Estimated Fair Value, Total	179,484
Unrealized Losses, Total	(828)
Mortgage-Backed Securities [Member]
Estimated Fair Value, less than 12 months, Available for Sale and Held To Maturity, Combined	107,468
Unrealized Losses, less than 12 months, Available for Sale and Held to Maturity, Combined	(415)
Estimated Fair Value, 12 months or longer, Available for Sale and Held to Maturity, Combined	0
Unrealized Losses, 12 months or longer, Available for Sale and Held to Maturity, Combined	0
Estimated Fair Value, Total	107,468
Unrealized Losses, Total	(415)
Debt Securities [Member]
Estimated Fair Value, Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	315,210
Unrealized Losses, Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(2,404)
Estimated Fair Value, Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	244,312
Unrealized Losses, Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses,	(29,143)
Estimated Fair Value, Total	559,522
Unrealized Losses, Total	(31,547)
Equity Securities [Member]
Estimated Fair Value, Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	13,181
Unrealized Losses, Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(2,440)
Estimated Fair Value, Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,393
Unrealized Losses, Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses,	(379)
Estimated Fair Value, Total	14,574
Unrealized Losses, Total	(2,819)
Auction Rate Securities [Member]
Estimated Fair Value, Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	13,794
Unrealized Losses, Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(403)
Estimated Fair Value, Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	197,235
Unrealized Losses, Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses,	(15,358)
Estimated Fair Value, Total	211,029
Unrealized Losses, Total	$ (15,761)