Loans and Asset Quality Information (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Covered purchased nonimpaired loans:
Carrying amount of nonimpaired covered loans, beginning balance	$ 277,489	$ 353,370
Principal repayments	(14,595)	(51,582)
Transfers to foreclosed real estate	(2,701)	(30,181)
Loan charge-offs	(5,109)	(10,584)
Accretion of loan discount	3,658	16,466
Balance, ending, carrying value	$ 258,742	$ 277,489