Investments And MBS (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Available-for-sale Securities and Held-to-maturity Securities [Abstract]
Amortized Cost	$ 1,486,357		$ 1,486,357		$ 1,452,258
AvailableForSaleSecuritiesGrossUnrealizedGainAccumulatedInInvestments	28,139		28,139		61,512
AvailableForSaleSecuritiesGrossUnrealizedLossAccumulatedInInvestments	16,119		16,119		613
Fair Value	1,498,377		1,498,377		1,513,157
Amortized Cost	175		175		206
HeldToMaturitySecuritiesGrossUnrealizedGainAccumulatedInInvestments	0		0		0
HeldToMaturitySecuritiesGrossUnrealizedLossesAccumulatedInInvestments	0		0		0
Fair Value	175		175		206
Gain (Loss) on Investments [Abstract]
Proceeds from Sales			0	506,150
Gross Realized Gains			0	12,666
Gross Realized Losses			0	(74)
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Market Value, Less than 12 months	502,499		502,499		0
Unrealized Losses, Less than 12 months	(15,351)		(15,351)		0
Market Value, 12 months or longer	12,551		12,551		12,921
Unrealized Losses, 12 months or longer	(768)		(768)		(613)
Market Value, Total	515,050		515,050		12,921
Unrealized Losses, Total	(16,119)		(16,119)		(613)
Other-than-temporary impairment credit losses on securities	0	0	0	6,819
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	175		175
Amortized Cost, Total	175		175		206
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	175		175
Fair Value	175		175		206
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	9,404		9,404
Amortized Cost, Due after five years through ten years	90,788		90,788
Amortized Cost, Due after ten years	1,386,165		1,386,165
Amortized Cost, Total	1,486,357		1,486,357
Estimated Fair Value, Due within one year	0		0
Estimated Fair Value, Due after one year through five years	9,954		9,954
Estimated Fair Value, Due after five years through ten years	90,357		90,357
Estimated Fair Value, Due after ten years	1,398,066		1,398,066
Fair Value	1,498,377		1,498,377		1,513,157
MBS
Available-for-sale Securities and Held-to-maturity Securities [Abstract]
Amortized Cost	1,300,288		1,300,288		1,263,786
AvailableForSaleSecuritiesGrossUnrealizedGainAccumulatedInInvestments	20,362		20,362		45,052
AvailableForSaleSecuritiesGrossUnrealizedLossAccumulatedInInvestments	15,194		15,194		0
Fair Value	1,305,456		1,305,456		1,308,838
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Market Value, Less than 12 months	497,736		497,736		0
Unrealized Losses, Less than 12 months	(15,194)		(15,194)		0
Market Value, 12 months or longer	0		0		0
Unrealized Losses, 12 months or longer	0		0		0
Market Value, Total	497,736		497,736		0
Unrealized Losses, Total	(15,194)		(15,194)		0
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Fair Value	1,305,456		1,305,456		1,308,838
Municipal Bonds
Available-for-sale Securities and Held-to-maturity Securities [Abstract]
Amortized Cost	185,907		185,907		188,467
AvailableForSaleSecuritiesGrossUnrealizedGainAccumulatedInInvestments	7,767		7,767		16,452
AvailableForSaleSecuritiesGrossUnrealizedLossAccumulatedInInvestments	925		925		613
Fair Value	192,749		192,749		204,306
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Market Value, Less than 12 months	4,763		4,763		0
Unrealized Losses, Less than 12 months	(157)		(157)		0
Market Value, 12 months or longer	12,551		12,551		12,921
Unrealized Losses, 12 months or longer	(768)		(768)		(613)
Market Value, Total	17,314		17,314		12,921
Unrealized Losses, Total	(925)		(925)		(613)
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Fair Value	192,749		192,749		204,306
Other
Available-for-sale Securities and Held-to-maturity Securities [Abstract]
Amortized Cost	162		162		5
AvailableForSaleSecuritiesGrossUnrealizedGainAccumulatedInInvestments	10		10		8
AvailableForSaleSecuritiesGrossUnrealizedLossAccumulatedInInvestments	0		0		0
Fair Value	172		172		13
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		0
Unrealized Losses, 12 months or longer	0		0		0
Market Value, Total	0		0		0
Unrealized Losses, Total	0		0		0
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Fair Value	172		172		13
Tax Credits
Available-for-sale Securities and Held-to-maturity Securities [Abstract]
Amortized Cost	175		175		206
HeldToMaturitySecuritiesGrossUnrealizedGainAccumulatedInInvestments	0		0		0
HeldToMaturitySecuritiesGrossUnrealizedLossesAccumulatedInInvestments	0		0		0
Fair Value	175		175		206
Held-to-maturity Securities, Debt Maturities [Abstract]
Fair Value	$ 175		$ 175		$ 206