Loans and the Allowance for Credit Losses - Summary of Changes in Allowance for Credit Losses (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance			$ 47,368	$ 52,699
Allowance for loan commitments, beginning balance			602	341
Total beginning allowance for credit losses			47,970	53,040
Provision for loan losses			3,114	3,147
Provision for loan commitments			(66)	(24)
Total provision for credit losses	849	1,021	3,048	3,123
Charge-offs			(6,639)	(7,063)
Recoveries			1,898	1,598
Net charge-offs			(4,741)	(5,465)
Allowance for loan losses, ending balance	45,741	50,381	45,741	50,381
Allowance for loan commitments, ending balance	536	317	536	317
Total ending allowance for credit losses	46,277	50,698	46,277	50,698
Commercial Real Estate - Land and Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance			6,056	3,741
Allowance for loan commitments, beginning balance			301	27
Total beginning allowance for credit losses			6,357	3,768
Provision for loan losses			(405)	559
Provision for loan commitments			(20)	11
Total provision for credit losses			(425)	570
Charge-offs				(373)
Recoveries				10
Net charge-offs				(363)
Allowance for loan losses, ending balance	5,651	3,937	5,651	3,937
Allowance for loan commitments, ending balance	281	38	281	38
Total ending allowance for credit losses	5,932	3,975	5,932	3,975
Commercial Real Estate - Improved Property [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance			18,157	23,614
Allowance for loan commitments, beginning balance			62	25
Total beginning allowance for credit losses			18,219	23,639
Provision for loan losses			(511)	1,855
Provision for loan commitments			(52)	(2)
Total provision for credit losses			(563)	1,853
Charge-offs			(728)	(1,395)
Recoveries			390	420
Net charge-offs			(338)	(975)
Allowance for loan losses, ending balance	17,308	24,494	17,308	24,494
Allowance for loan commitments, ending balance	10	23	10	23
Total ending allowance for credit losses	17,318	24,517	17,318	24,517
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance			9,925	9,326
Allowance for loan commitments, beginning balance			130	215
Total beginning allowance for credit losses			10,055	9,541
Provision for loan losses			1,870	(208)
Provision for loan commitments			1	(77)
Total provision for credit losses			1,871	(285)
Charge-offs			(2,384)	(919)
Recoveries			543	273
Net charge-offs			(1,841)	(646)
Allowance for loan losses, ending balance	9,954	8,472	9,954	8,472
Allowance for loan commitments, ending balance	131	138	131	138
Total ending allowance for credit losses	10,085	8,610	10,085	8,610
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance			5,673	7,182
Allowance for loan commitments, beginning balance			5	6
Total beginning allowance for credit losses			5,678	7,188
Provision for loan losses			575	87
Total provision for credit losses			575	87
Charge-offs			(1,207)	(1,573)
Recoveries			248	113
Net charge-offs			(959)	(1,460)
Allowance for loan losses, ending balance	5,289	5,809	5,289	5,809
Allowance for loan commitments, ending balance	5	6	5	6
Total ending allowance for credit losses	5,294	5,815	5,294	5,815
Home Equity [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance			2,017	2,458
Allowance for loan commitments, beginning balance			85	49
Total beginning allowance for credit losses			2,102	2,507
Provision for loan losses			392	(32)
Provision for loan commitments			5	44
Total provision for credit losses			397	12
Charge-offs			(348)	(346)
Recoveries			71	43
Net charge-offs			(277)	(303)
Allowance for loan losses, ending balance	2,132	2,123	2,132	2,123
Allowance for loan commitments, ending balance	90	93	90	93
Total ending allowance for credit losses	2,222	2,216	2,222	2,216
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance			5,020	5,557
Allowance for loan commitments, beginning balance			19	19
Total beginning allowance for credit losses			5,039	5,576
Provision for loan losses			642	836
Total provision for credit losses			642	836
Charge-offs			(1,610)	(2,043)
Recoveries			512	607
Net charge-offs			(1,098)	(1,436)
Allowance for loan losses, ending balance	4,564	4,957	4,564	4,957
Allowance for loan commitments, ending balance	19	19	19	19
Total ending allowance for credit losses	4,583	4,976	4,583	4,976
Deposit Overdraft [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance			520	821
Total beginning allowance for credit losses			520	821
Provision for loan losses			551	50
Total provision for credit losses			551	50
Charge-offs			(362)	(414)
Recoveries			134	132
Net charge-offs			(228)	(282)
Allowance for loan losses, ending balance	843	589	843	589
Total ending allowance for credit losses	$ 843	$ 589	$ 843	$ 589