Investments (Details 4) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses, Less Than 12 Months	$ (1,301)	$ (8,383)
Gross Unrealized Losses, 12 Months or More	(1,198)	(38)
Gross Unrealized Losses, Total	(2,499)	(8,421)
Fair Value, Less than 12 Months	178,170	386,371
Fair Value, 12 Months or More	22,175	8,384
Fair Value, Total	200,345	394,755
Unrealized Losses on Investment Securities
Held-to-maturity securities continuous unrealized loss position less than 12 months, Gross Unrealized Losses	(261)	(97)
Held-to-maturity securities continuous unrealized loss position less than 12 months, Fair Value	43,323	13,524
Held-to-maturity securities continuous unrealized loss position 12 months or more, Gross Unrealized Losses	0	0
Held-to-maturity securities continuous unrealized loss position 12 months or more, Fair Value	0	0
Held-to-maturity securities continuous unrealized loss position, Gross Unrealized Losses	(261)	(97)
Held-to-maturity securities, continuous unrealized loss position, Fair Value, Total	43,323	13,524
Agency MBS [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses, Less Than 12 Months	(696)	(5,321)
Gross Unrealized Losses, 12 Months or More	0	0
Gross Unrealized Losses, Total	(696)	(5,321)
Fair Value, Less than 12 Months	127,134	252,844
Fair Value, 12 Months or More	0	0
Fair Value, Total	127,134	252,844
Non-agency MBS [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses, Less Than 12 Months	(5)	(835)
Gross Unrealized Losses, 12 Months or More	(1,198)	(38)
Gross Unrealized Losses, Total	(1,203)	(873)
Fair Value, Less than 12 Months	1,841	20,905
Fair Value, 12 Months or More	22,175	8,384
Fair Value, Total	24,016	29,289
U.S. Treasury and agency securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses, Less Than 12 Months	(16)	(478)
Gross Unrealized Losses, 12 Months or More	0	0
Gross Unrealized Losses, Total	(16)	(478)
Fair Value, Less than 12 Months	19,780	20,151
Fair Value, 12 Months or More	0	0
Fair Value, Total	19,780	20,151
Corporate debt [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses, Less Than 12 Months	(15)
Gross Unrealized Losses, 12 Months or More	0
Gross Unrealized Losses, Total	(15)
Fair Value, Less than 12 Months	0
Fair Value, 12 Months or More	0
Fair Value, Total	0
Agency callable notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses, Less Than 12 Months	(569)	(1,749)
Gross Unrealized Losses, 12 Months or More	0	0
Gross Unrealized Losses, Total	(569)	(1,749)
Fair Value, Less than 12 Months	29,415	92,471
Fair Value, 12 Months or More	0	0
Fair Value, Total	$ 29,415	$ 92,471

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