Covered Assets and FDIC Loss-sharing Asset (Changes in Allowance for Covered Loans) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Covered Assets And FDIC Loss Sharing Asset [Line Items]
Provision for loan and lease losses	$ 20,185	$ (422)
Covered Loans [Member]
Covered Assets And FDIC Loss Sharing Asset [Line Items]
Beginning balance	4,944	6,055
Loans charged off	(562)	0
Recoveries	(437)	0
Provision for loan and lease losses	15,685	(422)
Ending balance	$ 20,504	$ 5,633