Loans and Allowance for Credit Losses - Schedule of Activity of Purchased Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Financing Receivable, Impaired [Line Items]
Purchased impaired loans	$ 39,825	$ 37,145
Carrying amount, net of allowance	38,063	34,576
Allowance for loan losses	1,762	2,569
Commercial Loan [Member]
Financing Receivable, Impaired [Line Items]
Purchased impaired loans	2,506	648
Allowance for loan losses	252	429
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Purchased impaired loans	27,654	23,618
Allowance for loan losses	1,255	2,025
Consumer Loan [Member]
Financing Receivable, Impaired [Line Items]
Purchased impaired loans	9,509	12,725
Allowance for loan losses	215	80
Residential [Member]
Financing Receivable, Impaired [Line Items]
Purchased impaired loans	156	154
Allowance for loan losses	$ 40	$ 35