Allowance for loan losses (Details 2) (USD $) In Thousands	3 Months Ended		6 Months Ended	12 Months Ended		3 Months Ended		6 Months Ended		12 Months Ended
	Mar. 31, 2011	Jun. 30, 2010	Jun. 30, 2010	Dec. 31, 2010	Jun. 30, 2011	Jun. 30, 2011 Covered Loans [Member]	Jun. 30, 2010 Covered Loans [Member]	Jun. 30, 2011 Covered Loans [Member]	Jun. 30, 2010 Covered Loans [Member]	Dec. 31, 2010 Covered Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	$ 114,690	$ 117,806	$ 115,092	$ 115,092	$ 109,187	$ 28,405	$ 0	$ 13,733	$ 0	$ 0
Provision for loan losses before benefit attributable to FDIC loss share agreements						15,156	461	35,666	461	27,184
Benefit attributable to FDIC loss share agreements						(7,675)	(193)	(22,854)	(193)	(22,752)
Net provision for loan losses, covered	15,200	20,366	45,859	83,783		7,481	268	12,812	268	4,432
Increase in indemnification asset						7,675	193	22,854	193	22,752
Loans charged off:		24,967	51,162	104,532		(10,201)	(220)	(16,039)	(220)	(13,451)
Balance at end of period		$ 118,343	$ 118,343	$ 114,690	$ 109,187	$ 33,360	$ 241	$ 33,360	$ 241	$ 13,733