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	Jun. 30, 2014
Estimated Fair Value, Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 79,302
Available-for-sale Securities, Continuous Unrealized Loss Position Less Than 12 Months, Aggregate Losses Accumulated In Investments	182
Estimated Fair Value, Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,204,192
Unrealized Losses, Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses,	(49,963)
Estimated Fair Value, Total	1,283,494
Available-for-sale Securities, Continuous Unrealized Loss Position Aggregate Losses Accumulated In Investments	50,145
Municipal Bonds [Member]
Estimated Fair Value, Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	8,531
Estimated Fair Value, Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	34,089
Estimated Fair Value, Total	42,620
Corporate Debt Securities [Member]
Estimated Fair Value, Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0
Estimated Fair Value, Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	42,995
Estimated Fair Value, Total	42,995
Collateralized Mortgage Obligations [Member]
Estimated Fair Value, Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	33,465
Estimated Fair Value, Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	677,357
Estimated Fair Value, Total	710,822
Collateralized Mortgage Backed Securities [Member]
Estimated Fair Value, Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	37,304
Estimated Fair Value, Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	302,835
Estimated Fair Value, Total	340,139
Auction Rate Securities [Member]
Estimated Fair Value, Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0
Estimated Fair Value, Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	146,839
Estimated Fair Value, Total	146,839
Debt Securities [Member]
Estimated Fair Value, Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	79,300
Estimated Fair Value, Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,204,115
Estimated Fair Value, Total	1,283,415
Equity Securities [Member]
Estimated Fair Value, Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	2
Estimated Fair Value, Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	77
Estimated Fair Value, Total	79
Equity Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position Less Than 12 Months, Aggregate Losses Accumulated In Investments	1
Available-for-sale Securities, Continuous Unrealized Loss Position 12 Months Or Longer, Aggregate Losses Accumulated In Investments	13
Available-for-sale Securities, Continuous Unrealized Loss Position Aggregate Losses Accumulated In Investments	14
Debt Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position Less Than 12 Months, Aggregate Losses Accumulated In Investments	181
Available-for-sale Securities, Continuous Unrealized Loss Position 12 Months Or Longer, Aggregate Losses Accumulated In Investments	49,950
Available-for-sale Securities, Continuous Unrealized Loss Position Aggregate Losses Accumulated In Investments	50,131
Auction Rate Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position Less Than 12 Months, Aggregate Losses Accumulated In Investments	0
Available-for-sale Securities, Continuous Unrealized Loss Position 12 Months Or Longer, Aggregate Losses Accumulated In Investments	11,533
Available-for-sale Securities, Continuous Unrealized Loss Position Aggregate Losses Accumulated In Investments	11,533
Collateralized Mortgage Backed Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position Less Than 12 Months, Aggregate Losses Accumulated In Investments	45
Available-for-sale Securities, Continuous Unrealized Loss Position 12 Months Or Longer, Aggregate Losses Accumulated In Investments	4,681
Available-for-sale Securities, Continuous Unrealized Loss Position Aggregate Losses Accumulated In Investments	4,726
Collateralized Mortgage Obligations [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position Less Than 12 Months, Aggregate Losses Accumulated In Investments	97
Available-for-sale Securities, Continuous Unrealized Loss Position 12 Months Or Longer, Aggregate Losses Accumulated In Investments	28,124
Available-for-sale Securities, Continuous Unrealized Loss Position Aggregate Losses Accumulated In Investments	28,221
Corporate Debt Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position Less Than 12 Months, Aggregate Losses Accumulated In Investments	0
Available-for-sale Securities, Continuous Unrealized Loss Position 12 Months Or Longer, Aggregate Losses Accumulated In Investments	4,862
Available-for-sale Securities, Continuous Unrealized Loss Position Aggregate Losses Accumulated In Investments	4,862
Municipal Bonds [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position Less Than 12 Months, Aggregate Losses Accumulated In Investments	39
Available-for-sale Securities, Continuous Unrealized Loss Position 12 Months Or Longer, Aggregate Losses Accumulated In Investments	750
Available-for-sale Securities, Continuous Unrealized Loss Position Aggregate Losses Accumulated In Investments	$ 789