Portfolio Loans Not Covered by Loss Share ("Non-covered") - Summary of Allowance for Loan Losses for Non-covered Loans by Portfolio Class and Category (Details) (Non-Covered Loans, USD $) In Thousands, unless otherwise specified	3 Months Ended
	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012
Allowance for Loan Losses [Roll Forward]
Balance	$ 36,304	$ 37,596	$ 37,989
Provision charged to expense	1,048	75	1,718
Losses charged off	(3,974)	(1,971)	(2,734)
Recoveries	844	604	623
Balance	34,222	36,304	37,596
Commercial & Industrial
Allowance for Loan Losses [Roll Forward]
Balance	8,981	12,385	11,945
Provision charged to expense	(204)	(3,201)	929
Losses charged off	(1,479)	(406)	(585)
Recoveries	142	203	96
Balance	7,440	8,981	12,385
Real Estate | Commercial Real Estate Owner Occupied
Allowance for Loan Losses [Roll Forward]
Balance	5,306	6,784	6,297
Provision charged to expense	(738)	(744)	1,231
Losses charged off	(625)	(739)	(746)
Recoveries	1	5	2
Balance	3,944	5,306	6,784
Real Estate | Commercial Real Estate Investor Owned
Allowance for Loan Losses [Roll Forward]
Balance	10,222	6,797	6,751
Provision charged to expense	604	3,518	216
Losses charged off	(639)	(108)	(185)
Recoveries	14	15	15
Balance	10,201	10,222	6,797
Real Estate | Construction and Land Development
Allowance for Loan Losses [Roll Forward]
Balance	5,449	5,412	5,847
Provision charged to expense	2,551	442	269
Losses charged off	(949)	(502)	(856)
Recoveries	15	97	152
Balance	7,066	5,449	5,412
Real Estate | Residential Real Estate
Allowance for Loan Losses [Roll Forward]
Balance	3,249	3,370	3,931
Provision charged to expense	(1,202)	(189)	(555)
Losses charged off	(282)	(216)	(362)
Recoveries	672	284	356
Balance	2,437	3,249	3,370
Consumer & Other
Allowance for Loan Losses [Roll Forward]
Balance	19	16	14
Provision charged to expense	4	3	0
Losses charged off	0	0	0
Recoveries	0	0	2
Balance	23	19	16
Qualitative Adjustment
Allowance for Loan Losses [Roll Forward]
Balance	3,078	2,832	3,204
Provision charged to expense	33	246	(372)
Losses charged off	0	0	0
Recoveries	0	0	0
Balance	$ 3,111	$ 3,078	$ 2,832