Income Taxes - Components of Deferred Tax Assets and Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Deferred tax assets:
Loan and lease loss	$ 8,785	$ 8,753
Deferred compensation	2,675	2,613
Actuarial adjustments on retirement benefits	4,568	7,551
Interest on nonaccrual loans	2,268	1,839
State net operating losses	1,743	1,441
Other-than-temporary impairments on equity securities	759	1,218
Alternative minimum tax credits	1,367	1,590
Net unrealized holding losses on securities available-for-sale	792
Other	280
Gross deferred tax assets	23,237	25,005
Valuation allowance	(1,630)	(1,432)
Total deferred tax asset, net of valuation allowance	21,607	23,573
Deferred tax liabilities:
Market discount	1,722	1,624
Retirement plans	5,602	5,100
Intangible assets	2,212	1,567
Net unrealized holding gains on securities available-for-sale and swaps		3,825
Other		60
Total deferred tax liabilities	9,536	12,176
Net deferred tax assets	$ 12,071	$ 11,397