Loans and Allowance for Loan Losses (Details 5) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Changes in allowance for loan losses
Balance at beginning of period	$ 76,510	$ 80,987
Loans charged-off	(4,607)	(5,698)
Recoveries of loans previously charged off	1,045	1,640
Net charge-offs	(3,562)	(4,058)
Provision for loan losses	(2)	5,033
Benefit attributable to FDIC loss share agreements	1,062	(2,310)
Total provision for loan losses charged to operations	1,060	2,723
Provision for loan losses recorded through the FDIC loss share receivable	(1,062)	2,310
Balance at end of period	72,946	81,962
Non-acquired loans
Changes in allowance for loan losses
Balance at beginning of period	44,378	49,367
Loans charged-off	(4,607)	(5,698)
Recoveries of loans previously charged off	1,045	1,640
Net charge-offs	(3,562)	(4,058)
Provision for loan losses	853	2,298
Total provision for loan losses charged to operations	853	2,298
Balance at end of period	41,669	47,607
Acquired loans
Changes in allowance for loan losses
Balance at beginning of period	32,132	31,620
Provision for loan losses	(855)	2,735
Benefit attributable to FDIC loss share agreements	1,062	(2,310)
Total provision for loan losses charged to operations	207	425
Provision for loan losses recorded through the FDIC loss share receivable	(1,062)	2,310
Balance at end of period	$ 31,277	$ 34,355