Loans and Allowance for Loan Losses (Details 9) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2012	Dec. 31, 2011
Covered loans [Member]
Changes in the carrying amount of covered acquired loans and accretable yield for loans receivable
Carrying Amount of Loans, Balance at beginning of period	$ 671,443	$ 809,459
Carrying Amount of Loans, Additions
Carrying Amount of Loans, Payments received, net	(107,893)	(193,432)
Carrying Amount of Loans, Accretion	12,392	55,416
Carrying Amount of Loans, Balance at end of period	575,942	671,443
Accretable Discount, Balance at beginning of period	153,137	107,638
Accretable Discount, Additions
Accretable Discount, Payments received, net
Accretable Discount, Accretion	(12,392)	(55,416)
Accretable Discount, Decrease in expected cash flows based on actual cash flow, loan sales and foreclosures assumptions	(1,542)	(18,930)
Accretable Discount, Net transfer from (to) nonaccretable difference to accretable yield	(17,014)	119,845
Accretable Discount, Balance at end of period	122,189	153,137
Non Covered [Member]
Changes in the carrying amount of covered acquired loans and accretable yield for loans receivable
Carrying Amount of Loans, Balance at beginning of period	339,452
Carrying Amount of Loans, Additions		535,489
Carrying Amount of Loans, Payments received, net	(40,083)	(206,306)
Carrying Amount of Loans, Accretion	8,000	10,269
Carrying Amount of Loans, Balance at end of period	307,369	339,452
Accretable Discount, Balance at beginning of period	130,691
Accretable Discount, Additions		132,136
Accretable Discount, Payments received, net
Accretable Discount, Accretion	(8,000)	(22,719)
Accretable Discount, Decrease in expected cash flows based on actual cash flow, loan sales and foreclosures assumptions	(18,609)	(26,630)
Accretable Discount, Net transfer from (to) nonaccretable difference to accretable yield	15,501	47,904
Accretable Discount, Balance at end of period	$ 119,583	$ 130,691