Covered Assets and FDIC Loss-sharing Asset (Analysis and Allowance for Losses on Covered Loans) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Jun. 30, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Dec. 31, 2010
Covered Assets And FDIC Loss Sharing Asset [Line Items]
Loans, net	$ 2,854,603		$ 2,827,259
Covered Loans [Member]
Covered Assets And FDIC Loss Sharing Asset [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	554,332		721,313
Valuation discount on covered loans	95,889		184,440
Allowance for loan losses	29,157	31,784	4,944	8,327	7,948	6,055
Loans, net	429,286		531,929
Commercial Portfolio Segment [Member] | Covered Loans [Member]
Covered Assets And FDIC Loss Sharing Asset [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	141,094		195,737
Real Estate Portfolio Segment [Member] | Covered Loans [Member]
Covered Assets And FDIC Loss Sharing Asset [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	320,238		390,636
Real Estate Portfolio Segment [Member] | Covered Loans [Member] | One-to-Four Family Residential [Member]
Covered Assets And FDIC Loss Sharing Asset [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	62,959		79,328
Real Estate Portfolio Segment [Member] | Covered Loans [Member] | Commercial and Multifamily Residential [Member]
Covered Assets And FDIC Loss Sharing Asset [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	257,279		311,308
Real Estate Construction Portfolio Segment [Member] | Covered Loans [Member]
Covered Assets And FDIC Loss Sharing Asset [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	46,468		78,063
Real Estate Construction Portfolio Segment [Member] | Covered Loans [Member] | One-to-Four Family Residential [Member]
Covered Assets And FDIC Loss Sharing Asset [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	29,774		54,402
Real Estate Construction Portfolio Segment [Member] | Covered Loans [Member] | Commercial and Multifamily Residential [Member]
Covered Assets And FDIC Loss Sharing Asset [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	16,694		23,661
Consumer Portfolio Segment [Member] | Covered Loans [Member]
Covered Assets And FDIC Loss Sharing Asset [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	$ 46,532		$ 56,877