Investments And MBS (Details) (USD $)	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Available-for-sale Securities and Held-to-maturity Securities [Abstract]
Amortized cost	$ 1,452,258,000		$ 2,485,642,000
Gross Unrealized Gains	61,512,000		69,100,000
Gross Unrealized Losses	(613,000)		(6,866,000)
Estimated Fair Value, Total	1,513,157,000		2,547,876,000
Amortized Cost	206,000		1,747,000
Gross Unrealized Gains	0		0
Gross Unrealized Losses	0		0
Fair Value	206,000		1,747,000
Gain (Loss) on Investments [Abstract]
Proceeds from Sales	879,174,000		586,340,000		1,056,677,000
Gross Realized Gains	24,024,000		18,771,000		35,546,000
Gross Realized Losses	189,000		2,535,000		9,804,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Market Value, Less than 12 months	0		1,419,000
Unrealized Losses, Less than 12 months	0		(12,000)
Market Value, 12 months or longer	12,921,000		61,494,000
Unrealized Losses, 12 months or longer	(613,000)		(6,854,000)
Market Value	12,921,000		62,913,000
Unrealized Losses	(613,000)		(6,866,000)
Held-to-maturity Securities, Debt Maturities [Abstract]
Amortized Cost, Due within one year	0
Amortized Cost, Due after one year through five years	0
Amortized Cost, Due afer five years through ten years	0
Amortized Cost, Due after ten years	206,000
Amortized Cost, Total	206,000
Estimated Fair Value, Due within one year	0
Estimated Fair Value, Due after one year through five years	0
Estimated Fair Value, Due after five years through ten years	0
Estimated Fair Value, Due after ten years	206,000
Estimated Fair Value, Total	206,000
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Amortized Cost, Due within on year	0
Amortized Cost, Due after one year through five years	3,033,000
Amortized Cost, Due after five years through ten years	70,704,000
Amortized Cost, Due after ten years	1,378,521,000
Amortized Cost, Total	1,452,258,000
Estimated Fair Value, Due within one year	0
Estimated Fair Value, Due after one year through five years	3,266,000
Estimated Fair Value, Due after five years through ten years	73,979,000
Estimated Fair Value, Due after ten years	1,435,912,000
Estimated Fair Value, Total	1,513,157,000		2,547,876,000
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
OTTI, Beginning Balance	0		0		0
Additions	6,819,000	[1]	0	[1]	0	[1]
Realized	(6,819,000)		0		0
OTTI, Ending Balance	0		0		0
Gain (Loss) on Investments, Excluding Other than Temporary Impairments	2,500,000
MBS
Available-for-sale Securities and Held-to-maturity Securities [Abstract]
Amortized cost	1,263,786,000		2,265,207,000
Gross Unrealized Gains	45,052,000		55,760,000
Gross Unrealized Losses	0		(33,000)
Estimated Fair Value, Total	1,308,838,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Market Value, Less than 12 months	0		1,419,000
Unrealized Losses, Less than 12 months	0		(12,000)
Market Value, 12 months or longer	0		24,726,000
Unrealized Losses, 12 months or longer	0		(21,000)
Market Value	0		26,145,000
Unrealized Losses	0		(33,000)
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Estimated Fair Value, Total	1,308,838,000
Municipal Bonds
Available-for-sale Securities and Held-to-maturity Securities [Abstract]
Amortized cost	188,467,000		195,512,000
Gross Unrealized Gains	16,452,000		13,338,000
Gross Unrealized Losses	(613,000)		(1,394,000)
Estimated Fair Value, Total	204,306,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Market Value, Less than 12 months	0		0
Unrealized Losses, Less than 12 months	0		0
Market Value, 12 months or longer	12,921,000		17,289,000
Unrealized Losses, 12 months or longer	(613,000)		(1,394,000)
Market Value	12,921,000		17,289,000
Unrealized Losses	(613,000)		(1,394,000)
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Estimated Fair Value, Total	204,306,000
Tax credits
Available-for-sale Securities and Held-to-maturity Securities [Abstract]
Amortized Cost	206,000		1,747,000
Gross Unrealized Gains	0		0
Gross Unrealized Losses	0		0
Fair Value	206,000		1,747,000
Other
Available-for-sale Securities and Held-to-maturity Securities [Abstract]
Amortized cost	5,000		24,923,000
Gross Unrealized Gains	8,000		2,000
Gross Unrealized Losses	0		(5,439,000)
Estimated Fair Value, Total	13,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Market Value, Less than 12 months	0		0
Unrealized Losses, Less than 12 months	0		0
Market Value, 12 months or longer	0		19,479,000
Unrealized Losses, 12 months or longer	0		(5,439,000)
Market Value	0		19,479,000
Unrealized Losses	0		(5,439,000)
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Estimated Fair Value, Total	$ 13,000

[1] The other-than-temporary impairment recognized in earnings during 2012 did not have a portion recognized in accumulated other comprehensive income.