Investment Securities - Securities with Other-than-Temporary-Impairment (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended		12 Months Ended
	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Total other-than-temporary-impairment recognized in earnings	$ 780		$ 876	$ 1,414	$ 1,409	$ 3,927	$ 24,795
Amount of other-than-temporary-impairment recognized in earnings	780		876	1,414	1,409	3,927	24,795
Life-to-date		31,545
Non Agency Residential Mortgage Backed Securities [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Total other-than-temporary-impairment recognized in earnings	619		715
Amortized Cost	44,404		44,404
Non Agency Residential 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		CCC
Total other-than-temporary-impairment recognized in earnings	84		160
Amortized Cost	13,176		13,176
Non Agency Residential Mortgage Backed Securities [Member] | CWALT Ser 73CB [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Debt Issuance Year			2005
Lowest Credit Rating	D		D
Total other-than-temporary-impairment recognized in earnings	117		117
Amortized Cost	2,772		2,772
Non Agency Residential Mortgage Backed Securities [Member] | HALO Ser 1R [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Debt Issuance Year			2006
Lowest Credit Rating	B		B
Total other-than-temporary-impairment recognized in earnings	129		133
Amortized Cost	15,470		15,470
Non Agency Residential 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		CCC
Total other-than-temporary-impairment recognized in earnings	142		142
Amortized Cost	9,567		9,567
Non Agency Residential Mortgage Backed Securities [Member] | RFMSI Ser S10 [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Debt Issuance Year			2006
Lowest Credit Rating	D		D
Total other-than-temporary-impairment recognized in earnings	147		163
Amortized Cost	3,419		3,419
Pooled Trust Preferred Securities Group 1 [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Total other-than-temporary-impairment recognized in earnings	161		161
Amortized Cost	4,017		4,017
Pooled Trust Preferred Securities Group 1 [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		D
Total other-than-temporary-impairment recognized in earnings	161		161
Amortized Cost	4,017		4,017
Mortgage Backed Securities Non Agency Group 2 [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Amortized Cost		13,603
Amount of other-than-temporary-impairment recognized in earnings				938	521	2,997	4,429
Life-to-date		8,885
Mortgage Backed Securities Non Agency Group 2 [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
Amortized Cost		10,753
Amount of other-than-temporary-impairment recognized in earnings				299		79	63
Life-to-date		441
Mortgage Backed Securities Non Agency Group 2 [Member] | CWALT Ser 73CB [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Debt Issuance Year		2005
Amount of other-than-temporary-impairment recognized in earnings				151		207	83
Life-to-date		441
Mortgage Backed Securities Non Agency Group 2 [Member] | HALO Ser 1R [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Debt Issuance Year		2006
Amount of other-than-temporary-impairment recognized in earnings				133	16
Life-to-date		149
Mortgage Backed Securities Non Agency Group 2 [Member] | RAST A9 [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Debt Issuance Year		2004
Amount of other-than-temporary-impairment recognized in earnings				142
Life-to-date		142
Mortgage Backed Securities Non Agency Group 2 [Member] | RFMSI Ser S10 [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Debt Issuance Year		2006
Lowest Credit Rating		D
Amortized Cost		2,850
Amount of other-than-temporary-impairment recognized in earnings				178	165	76	249
Life-to-date		668
Mortgage Backed Securities Non Agency Group 2 [Member] | CWALT Ser 73CB [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Debt Issuance Year		2005
Amount of other-than-temporary-impairment recognized in earnings				35		427	182
Life-to-date		644
Mortgage Backed Securities Non Agency Group 2 [Member] | CWHL 2006-10 [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Debt Issuance Year		2006
Amount of other-than-temporary-impairment recognized in earnings						309	762
Life-to-date		1,071
Mortgage Backed Securities Non Agency Group 2 [Member] | CWHL 2005-20 [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Debt Issuance Year		2005
Amount of other-than-temporary-impairment recognized in earnings						39	72
Life-to-date		111
Mortgage Backed Securities Non Agency Group 2 [Member] | FHASI Ser 4 [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Debt Issuance Year		2007
Amount of other-than-temporary-impairment recognized in earnings					340	629	223
Life-to-date		1,192
Mortgage Backed Securities Non Agency Group 2 [Member] | RFMSI Ser S9 [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Debt Issuance Year		2006
Amount of other-than-temporary-impairment recognized in earnings						923	1,880
Life-to-date		2,803
Mortgage Backed Securities Non Agency Group 2 [Member] | RALI QS2 [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Debt Issuance Year		2006
Amount of other-than-temporary-impairment recognized in earnings						278	739
Life-to-date		1,017
Mortgage Backed Securities Non Agency Group 2 [Member] | RFMSI Ser S10 [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Debt Issuance Year		2006
Amount of other-than-temporary-impairment recognized in earnings						30	176
Life-to-date		206
Pooled Trust Preferred Securities Group 2 [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Amortized Cost		8,775
Amount of other-than-temporary-impairment recognized in earnings				476	888	930	20,366
Life-to-date		22,660
Pooled Trust Preferred Securities Group 2 [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
Amortized Cost		4,012
Amount of other-than-temporary-impairment recognized in earnings				165		321	5,199
Life-to-date		5,685
Pooled Trust Preferred Securities Group 2 [Member] | TROPC [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Debt Issuance Year		2003
Amount of other-than-temporary-impairment recognized in earnings					888	444	3,517
Life-to-date		4,849
Pooled Trust Preferred Securities Group 2 [Member] | MM Community Funding IX [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Debt Issuance Year		2003
Lowest Credit Rating		CC
Amortized Cost		2,067
Amount of other-than-temporary-impairment recognized in earnings						165	2,612
Life-to-date		2,777
Pooled Trust Preferred Securities Group 2 [Member] | Pretsl XII [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Debt Issuance Year		2003
Lowest Credit Rating		C
Amortized Cost		2,696
Amount of other-than-temporary-impairment recognized in earnings							1,897
Life-to-date		1,897
Pooled Trust Preferred Securities Group 2 [Member] | Pretsl XV [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Debt Issuance Year		2004
Amount of other-than-temporary-impairment recognized in earnings							3,374
Life-to-date		3,374
Pooled Trust Preferred Securities Group 2 [Member] | Reg Div Funding 2005 [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Debt Issuance Year		2005
Amount of other-than-temporary-impairment recognized in earnings				311			3,767
Life-to-date		$ 4,078