Loans and Allowance for Credit Losses - Schedule of Impaired Loans that are Individually Evaluated (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Financing Receivable, Impaired [Line Items]
Recorded Investment, Total Loans	$ 75,588	$ 64,849
Unpaid Principal Balance, Total Loans	84,895	75,893
Related Allowance	9,093	7,068
Commercial Loan [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment with no related allowance	17,235	17,066
Unpaid Principal Balance with no related allowance	17,542	17,417
Recorded Investment with related allowance	12,807	9,282
Unpaid Principal Balance with related allowance	15,831	12,304
Related Allowance	6,105	4,723
Commercial Real Estate-Construction [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment with no related allowance	1,488	525
Unpaid Principal Balance with no related allowance	1,596	633
Recorded Investment with related allowance
Unpaid Principal Balance with related allowance
Related Allowance
Commercial Real Estate-Other [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment with no related allowance	19,334	15,746
Unpaid Principal Balance with no related allowance	24,295	22,550
Recorded Investment with related allowance	20,973	18,726
Unpaid Principal Balance with related allowance	21,744	19,358
Related Allowance	2,818	2,190
Consumer Loan [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment with no related allowance	335	324
Unpaid Principal Balance with no related allowance	353	342
Recorded Investment with related allowance	1,077	835
Unpaid Principal Balance with related allowance	1,124	888
Related Allowance	57	43
Residential [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment with no related allowance	98	106
Unpaid Principal Balance with no related allowance	99	106
Recorded Investment with related allowance	2,241	2,239
Unpaid Principal Balance with related allowance	2,311	2,295
Related Allowance	$ 113	$ 112