Loans and Other Repossessed Assets Acquired (Detail) - Commercial Credit Quality (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Pass [Member] | Commercial Loan [Member]
Commercial Credit Quality	$ 449,159	[1]	$ 448,856	[1]
Pass [Member] | Commercial Business [Member]
Commercial Credit Quality	92,495	[1]	77,326	[1]
Pass [Member] | Commercial Real Estate [Member]
Commercial Credit Quality	337,052	[1]	349,981	[1]
Pass [Member] | Commercial Construction [Member]
Commercial Credit Quality	1,092	[1]	817	[1]
Pass [Member] | Commercial Land [Member]
Commercial Credit Quality	18,520	[1]	20,732	[1]
Special Mention [Member] | Commercial Loan [Member]
Commercial Credit Quality	45,349	[1]	46,554	[1]
Special Mention [Member] | Commercial Business [Member]
Commercial Credit Quality	2,991	[1]	2,608	[1]
Special Mention [Member] | Commercial Real Estate [Member]
Commercial Credit Quality	26,665	[1]	27,523	[1]
Special Mention [Member] | Commercial Construction [Member]
Commercial Credit Quality	0	[1]	0	[1]
Special Mention [Member] | Commercial Land [Member]
Commercial Credit Quality	15,693	[1]	16,423	[1]
Substandard [Member] | Commercial Loan [Member]
Commercial Credit Quality	75,334	[1]	84,976	[1]
Substandard [Member] | Commercial Business [Member]
Commercial Credit Quality	9,714	[1]	10,988	[1]
Substandard [Member] | Commercial Real Estate [Member]
Commercial Credit Quality	57,024	[1]	64,610	[1]
Substandard [Member] | Commercial Construction [Member]
Commercial Credit Quality	0	[1]	247	[1]
Substandard [Member] | Commercial Land [Member]
Commercial Credit Quality	8,596	[1]	9,131	[1]
Doubtful [Member] | Commercial Loan [Member]
Commercial Credit Quality	0	[1]	0	[1]
Doubtful [Member] | Commercial Business [Member]
Commercial Credit Quality	0	[1]	0	[1]
Doubtful [Member] | Commercial Real Estate [Member]
Commercial Credit Quality	0	[1]	0	[1]
Doubtful [Member] | Commercial Construction [Member]
Commercial Credit Quality	0	[1]	0	[1]
Doubtful [Member] | Commercial Land [Member]
Commercial Credit Quality	0	[1]	0	[1]
Total Commercial Loans [Member] | Commercial Loan [Member]
Commercial Credit Quality	569,842	[1]	580,386	[1]
Total Commercial Loans [Member] | Commercial Business [Member]
Commercial Credit Quality	105,200	[1]	90,922	[1]
Total Commercial Loans [Member] | Commercial Real Estate [Member]
Commercial Credit Quality	420,741	[1]	442,114	[1]
Total Commercial Loans [Member] | Commercial Construction [Member]
Commercial Credit Quality	1,092	[1]	1,064	[1]
Total Commercial Loans [Member] | Commercial Land [Member]
Commercial Credit Quality	42,809	[1]	46,286	[1]
ASC 310-30 Loans [Member] | Commercial Loan [Member]
Commercial Credit Quality	93,891	[1]	100,733	[1]
ASC 310-30 Loans [Member] | Commercial Business [Member]
Commercial Credit Quality	24,969	[1]	27,457	[1]
ASC 310-30 Loans [Member] | Commercial Real Estate [Member]
Commercial Credit Quality	47,149	[1]	49,453	[1]
ASC 310-30 Loans [Member] | Commercial Construction [Member]
Commercial Credit Quality	0	[1]	0	[1]
ASC 310-30 Loans [Member] | Commercial Land [Member]
Commercial Credit Quality	21,773	[1]	23,823	[1]
Commercial Loan [Member]
Commercial Credit Quality	663,733	[1]	681,119	[1]
Commercial Business [Member]
Commercial Credit Quality	130,169	[1]	118,379	[1]
Commercial Real Estate [Member]
Commercial Credit Quality	467,890	[1]	491,567	[1]
Commercial Construction [Member]
Commercial Credit Quality	1,092	[1]	1,064	[1]
Commercial Land [Member]
Commercial Credit Quality	$ 64,582	[1]	$ 70,109	[1]

[1] Credit quality indicators are reviewed and updated as applicable on an ongoing basis in accordance with credit policies.