Investments And MBS (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Available-for-sale Securities and Held-to-maturity Securities [Abstract]
Amortized Cost	$ 1,964,414		$ 1,964,414		$ 2,485,642
Gross Unrealized Gains	86,075		86,075		69,100
Gross Unrealized Losses	(528)		(528)		(6,866)
Estimated Fair Value, Total	2,049,961		2,049,961		2,547,876
Amortized Cost	1,716		1,716		1,747
Gross Unrealized Gains	0		0		0
Gross Unrealized Losses	0		0		0
Fair Value	1,716		1,716		1,747
Gain (Loss) on Investments [Abstract]
Proceeds from Sales			506,150	384,431
Gross Realized Gains			12,666	16,605
Gross Realized Losses			(74)	(2,307)
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Market Value, Less than 12 months	0		0		1,419
Unrealized Losses, Less than 12 months	0		0		(12)
Market Value, 12 months or longer	12,664		12,664		61,494
Unrealized Losses, 12 months or longer	(528)		(528)		(6,854)
Market Value, Total	12,664		12,664		62,913
Unrealized Losses, Total	(528)		(528)		(6,866)
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Estimated Fair Value, Total	2,049,961		2,049,961		2,547,876
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
OTTI, Beginning Balance	6,819	0	0	0
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Additions, Additional Credit Losses	0	0	6,819	0
OTTI, Ending Balance	6,819	0	6,819	0
MBS [Member]
Available-for-sale Securities and Held-to-maturity Securities [Abstract]
Amortized Cost	1,757,584		1,757,584		2,265,207
Gross Unrealized Gains	67,864		67,864		55,760
Gross Unrealized Losses	0		0		(33)
Estimated Fair Value, Total	1,825,448		1,825,448
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Market Value, Less than 12 months	0		0		1,419
Unrealized Losses, Less than 12 months	0		0		(12)
Market Value, 12 months or longer	0		0		24,726
Unrealized Losses, 12 months or longer	0		0		(21)
Market Value, Total	0		0		26,145
Unrealized Losses, Total	0		0		(33)
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Estimated Fair Value, Total	1,825,448		1,825,448
Municipal Bonds [Member]
Available-for-sale Securities and Held-to-maturity Securities [Abstract]
Amortized Cost	188,579		188,579		195,512
Gross Unrealized Gains	17,354		17,354		13,338
Gross Unrealized Losses	(528)		(528)		(1,394)
Estimated Fair Value, Total	205,405		205,405
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Market Value, Less than 12 months	0		0		0
Unrealized Losses, Less than 12 months	0		0		0
Market Value, 12 months or longer	12,664		12,664		17,289
Unrealized Losses, 12 months or longer	(528)		(528)		(1,394)
Market Value, Total	12,664		12,664		17,289
Unrealized Losses, Total	(528)		(528)		(1,394)
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Estimated Fair Value, Total	205,405		205,405
Single issuer trust, preferred security, JP Morgan Chase [Member]
Available-for-sale Securities and Held-to-maturity Securities [Abstract]
Amortized Cost	27,500		27,500
Tax credits [Member]
Available-for-sale Securities and Held-to-maturity Securities [Abstract]
Amortized Cost	1,716		1,716		1,747
Gross Unrealized Gains	0		0		0
Gross Unrealized Losses	0		0		0
Fair Value	1,716		1,716		1,747
Other [Member]
Available-for-sale Securities and Held-to-maturity Securities [Abstract]
Amortized Cost	18,251		18,251		24,923
Gross Unrealized Gains	857		857		2
Gross Unrealized Losses	0		0		(5,439)
Estimated Fair Value, Total	19,108		19,108
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Market Value, Less than 12 months	0		0		0
Unrealized Losses, Less than 12 months	0		0		0
Market Value, 12 months or longer	0		0		19,479
Unrealized Losses, 12 months or longer	0		0		(5,439)
Market Value, Total	0		0		19,479
Unrealized Losses, Total	0		0		(5,439)
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Estimated Fair Value, Total	19,108		19,108
Held-to-maturity Securities [Member]
Held-to-maturity Securities, Debt Maturities [Abstract]
Amortized Cost, Due within one year	0		0
Amortized Cost, Due after one year through five years	0		0
Amortized Cost, Due afer five years through ten years	0		0
Amortized Cost, Due after ten years	1,716		1,716
Amortized Cost, Total	1,716		1,716
Estimated Fair Value, Due within one year	0		0
Estimated Fair Value, Due after one year through five years	0		0
Estimated Fair Value, Due after five years through ten years	0		0
Estimated Fair Value, Due after ten years	1,716		1,716
Estimated Fair Value, Total	1,716		1,716
Available-for-sale Securities [Member]
Available-for-sale Securities and Held-to-maturity Securities [Abstract]
Estimated Fair Value, Total	2,049,961		2,049,961
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Amortized Cost, Due within on year	0		0
Amortized Cost, Due after one year through five years	0		0
Amortized Cost, Due after five years through ten years	134,019		134,019
Amortized Cost, Due after ten years	1,830,395		1,830,395
Amortized Cost, Total	1,964,414		1,964,414
Estimated Fair Value, Due within one year	0		0
Estimated Fair Value, Due after one year through five years	0		0
Estimated Fair Value, Due after five years through ten years	138,991		138,991
Estimated Fair Value, Due after ten years	1,910,970		1,910,970
Estimated Fair Value, Total	$ 2,049,961		$ 2,049,961