Investment Securities (Securities With Other-Than-Temporary-Impairment) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended				12 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011		Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Amortized Cost	$ 2,155,885				$ 2,155,885				$ 2,030,801
Total other-than-temporary-impairment recognized in earnings	780		200		876		499		1,409	3,927	24,795
Non-agency Mortgage-Backed Securities [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Amortized Cost	44,404		40,955		44,404		40,955
Total other-than-temporary-impairment recognized in earnings	619		200		715		499
Non-agency Mortgage-Backed Securities [Member] | BAFC Ser 4 [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Debt Issuance Year	2007
Lowest Credit Rating	CCC	[1]			CCC	[1]
Amortized Cost	13,176				13,176
Total other-than-temporary-impairment recognized in earnings	84				160
Non-agency Mortgage-Backed Securities [Member] | CWALT Ser 73 CB [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Debt Issuance Year	2005
Lowest Credit Rating	D	[1]			D	[1]
Amortized Cost	2,772				2,772
Total other-than-temporary-impairment recognized in earnings	117				117
Non-agency Mortgage-Backed Securities [Member] | HALO Ser 1R [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Debt Issuance Year	2006		2006
Lowest Credit Rating	B	[1]	B	[1]	B	[1]	B	[1]
Amortized Cost	15,470		15,640		15,470		15,640
Total other-than-temporary-impairment recognized in earnings	129		16		133		16
Non-agency Mortgage-Backed Securities [Member] | RAST A9 [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Debt Issuance Year	2004
Lowest Credit Rating	CCC	[1]			CCC	[1]
Amortized Cost	9,567				9,567
Total other-than-temporary-impairment recognized in earnings	142				142
Non-agency Mortgage-Backed Securities [Member] | FHASI Ser 4 [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Debt Issuance Year			2007
Lowest Credit Rating			CC	[1]			CC	[1]
Amortized Cost			21,098				21,098
Total other-than-temporary-impairment recognized in earnings			138				340
Non-agency Mortgage-Backed Securities [Member] | RFMSI Ser S10 [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Debt Issuance Year	2006		2006
Lowest Credit Rating	D	[1]	CC	[1]	D	[1]	CC	[1]
Amortized Cost	3,419		4,217		3,419		4,217
Total other-than-temporary-impairment recognized in earnings	147		46		163		143
Non-agency Mortgage-Backed Securities [Member] | Reg Div Funding 2004 [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Debt Issuance Year	2004
Lowest Credit Rating	D	[1]			D	[1]
Amortized Cost	4,017				4,017
Total other-than-temporary-impairment recognized in earnings	161				161
Life To Date [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Total other-than-temporary-impairment recognized in earnings					$ 31,007

[1] Lowest rating for the security provided by any nationally recognized credit rating agency.