Loans and Other Repossessed Assets Acquired (Detail) - Analysis of changes in allowance for loan losses (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Balance at beginning of period	$ 44,179	$ 53,524
Provision for loan losses before benefit from FDIC loss share agreements	9,311
Benefit from FDIC loss share agreements	(3,339)
Provision for loan losses	5,972	6,745
Increase in FDIC indemnification asset	3,339
Loan charge-offs	(7,276)	(10,071)
Recoveries	1,213	578
Net charge-offs	(6,063)	(9,493)
Balance at end of period	47,427	50,776
Loans as of March 31, 2013
Individually evaluated for impairment	34,827	24,475
Collectively evaluated for impairment	2,321,555	2,322,309
ASC 310-30 loans	119,760	8,783
Total loans	2,476,142	2,355,567	2,495,324
Residential Loans [Member]
Balance at beginning of period	7,790	8,748
Provision for loan losses before benefit from FDIC loss share agreements	1,669
Benefit from FDIC loss share agreements	(250)
Provision for loan losses	1,419	41
Increase in FDIC indemnification asset	250
Loan charge-offs	(1,120)	(1,253)
Recoveries	49	45
Net charge-offs	(1,071)	(1,208)
Balance at end of period	8,388	7,581
Loans as of March 31, 2013
Individually evaluated for impairment	6,497	2,698
Collectively evaluated for impairment	1,016,540	1,026,214
ASC 310-30 loans	14,822	264
Total loans	1,037,859	1,029,176	1,031,533
Consumer Loan [Member]
Balance at beginning of period	20,403	22,581
Provision for loan losses before benefit from FDIC loss share agreements	2,148
Benefit from FDIC loss share agreements	(5)
Provision for loan losses	2,143	4,370
Increase in FDIC indemnification asset	5
Loan charge-offs	(3,237)	(4,802)
Recoveries	628	241
Net charge-offs	(2,609)	(4,561)
Balance at end of period	19,942	22,390
Loans as of March 31, 2013
Individually evaluated for impairment	9,105	5,683
Collectively evaluated for impairment	754,398	713,870
ASC 310-30 loans	11,047	370
Total loans	774,550	719,923	782,672
Commercial Business [Member]
Balance at beginning of period	3,066	4,106
Provision for loan losses before benefit from FDIC loss share agreements	1,833
Benefit from FDIC loss share agreements	(145)
Provision for loan losses	1,688	719
Increase in FDIC indemnification asset	145
Loan charge-offs	(352)	(887)
Recoveries	83	62
Net charge-offs	(269)	(825)
Balance at end of period	4,630	4,000
Loans as of March 31, 2013
Individually evaluated for impairment	2,009	2,181
Collectively evaluated for impairment	103,191	85,138
ASC 310-30 loans	24,969	735
Total loans	130,169	88,054
Commercial Real Estate [Member]
Balance at beginning of period	10,099	11,711
Provision for loan losses before benefit from FDIC loss share agreements	3,068
Benefit from FDIC loss share agreements	(1,621)
Provision for loan losses	1,447	567
Increase in FDIC indemnification asset	1,621
Loan charge-offs	(2,401)	(1,624)
Recoveries	312	162
Net charge-offs	(2,089)	(1,462)
Balance at end of period	11,078	10,816
Loans as of March 31, 2013
Individually evaluated for impairment	13,750	11,111
Collectively evaluated for impairment	406,991	430,553
ASC 310-30 loans	47,149	5,675
Total loans	467,890	447,339
Commercial Construction [Member]
Balance at beginning of period	16	397
Provision for loan losses before benefit from FDIC loss share agreements	19
Benefit from FDIC loss share agreements	0
Provision for loan losses	19	2
Increase in FDIC indemnification asset	0
Loan charge-offs	(36)	0
Recoveries	32	2
Net charge-offs	(4)	2
Balance at end of period	31	401
Loans as of March 31, 2013
Individually evaluated for impairment	0	261
Collectively evaluated for impairment	1,092	16,028
ASC 310-30 loans	0	0
Total loans	1,092	16,289
Commercial Land [Member]
Balance at beginning of period	2,805	5,981
Provision for loan losses before benefit from FDIC loss share agreements	574
Benefit from FDIC loss share agreements	(1,318)
Provision for loan losses	(744)	1,046
Increase in FDIC indemnification asset	1,318
Loan charge-offs	(130)	(1,505)
Recoveries	109	66
Net charge-offs	(21)	(1,439)
Balance at end of period	3,358	5,588
Loans as of March 31, 2013
Individually evaluated for impairment	3,466	2,541
Collectively evaluated for impairment	39,343	50,506
ASC 310-30 loans	21,773	1,739
Total loans	$ 64,582	$ 54,786