Income Taxes - Components of Pre-tax Income and Comprehensive Provision for Income Taxes (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Provision for income taxes:
Deferred income tax expense (benefit)	$ 468	$ 916	$ (7,713)
Tax provision attributable to continuing operations	5,012	3,226	1,415
Tax provision attributable to continuing operations	5,012	3,226	1,415
Comprehensive provision for income tax allocable to:
Tax provision attributable to continuing operations	5,012	3,226	1,415
Discontinued operations			3,484
Tax Provision Excluding Discontinued Operations
Provision for income taxes:
Currently payable	4,544	2,310	1,633
Deferred income tax expense (benefit)	468	916	(218)
Tax provision attributable to continuing operations	5,012	3,226	1,415
Expected tax expense, at the U.S. federal statutory income tax rate of 35%	4,787	3,234	1,729
State income taxes and other, net	627	294	173
Tax credits	(378)	(200)	(170)
Valuation allowance	(24)	(102)	(317)
Tax provision attributable to continuing operations	5,012	3,226	1,415
Comprehensive provision for income tax allocable to:
Tax provision attributable to continuing operations	5,012	3,226	1,415
Discontinued operations			5,397
Total	$ 5,012	$ 3,226	$ 6,812