Investments And MBS (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Available-for-sale Securities and Held-to-maturity Securities [Abstract]
Amortized Cost	$ 2,046,826		$ 2,046,826		$ 2,485,642
Gross Unrealized Gains	72,957		72,957		69,100
Gross Unrealized Losses	(775)		(775)		(6,866)
Estimated Fair Value, Total	2,119,008		2,119,008		2,547,876
Amortized Cost	1,726		1,726		1,747
Gross Unrealized Gains	0		0		0
Gross Unrealized Losses	0		0		0
Fair Value	1,726		1,726		1,747
Gain (Loss) on Investments [Abstract]
Proceeds from Sales			362,871	384,431
Gross Realized Gains			9,537	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	14,609		14,609		61,494
Unrealized Losses, 12 months or longer	(774)		(774)		(6,854)
Market Value, Total	14,609		14,609		62,913
Unrealized Losses, Total	(774)		(774)		(6,866)
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Estimated Fair Value, Total	2,119,008		2,119,008		2,547,876
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
OTTI, Beginning Balance	0	0	0	0
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Additions, Additional Credit Losses	6,819	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	1,839,894		1,839,894		2,265,207
Gross Unrealized Gains	57,416		57,416		55,760
Gross Unrealized Losses	0		0		(33)
Estimated Fair Value, Total	1,897,310		1,897,310
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	1,897,310		1,897,310
Municipal Bonds [Member]
Available-for-sale Securities and Held-to-maturity Securities [Abstract]
Amortized Cost	188,776		188,776		195,512
Gross Unrealized Gains	15,535		15,535		13,338
Gross Unrealized Losses	(774)		(774)		(1,394)
Estimated Fair Value, Total	203,537		203,537
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	14,609		14,609		17,289
Unrealized Losses, 12 months or longer	(774)		(774)		(1,394)
Market Value, Total	14,609		14,609		17,289
Unrealized Losses, Total	(774)		(774)		(1,394)
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Estimated Fair Value, Total	203,537		203,537
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
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Available-for-sale Securities, Basis for Valuation, Other than Equity Securities1	18,150		18,150
Tax credits [Member]
Available-for-sale Securities and Held-to-maturity Securities [Abstract]
Amortized Cost	1,726		1,726		1,747
Gross Unrealized Gains	0		0		0
Gross Unrealized Losses	0		0		0
Fair Value	1,726		1,726		1,747
Other [Member]
Available-for-sale Securities and Held-to-maturity Securities [Abstract]
Amortized Cost	18,156		18,156		24,923
Gross Unrealized Gains	6		6		2
Gross Unrealized Losses	(1)		(1)		(5,439)
Estimated Fair Value, Total	18,161		18,161
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	18,161		18,161
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	1,726		1,726
Amortized Cost, Total	1,726		1,726
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	1,726		1,726
Estimated Fair Value, Total	1,726		1,726
Available-for-sale Securities [Member]
Available-for-sale Securities and Held-to-maturity Securities [Abstract]
Estimated Fair Value, Total	2,119,008		2,119,008
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	780		780
Amortized Cost, Due after five years through ten years	136,113		136,113
Amortized Cost, Due after ten years	1,909,933		1,909,933
Amortized Cost, Total	2,046,826		2,046,826
Estimated Fair Value, Due within one year	0		0
Estimated Fair Value, Due after one year through five years	780		780
Estimated Fair Value, Due after five years through ten years	139,905		139,905
Estimated Fair Value, Due after ten years	1,978,323		1,978,323
Estimated Fair Value, Total	$ 2,119,008		$ 2,119,008