Stockholders' Equity - Changes in Stockholders' Equity (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at January 1, 2015			$ 279,059
Net income for the nine months ended September 30, 2015	$ 4,220	$ 4,652	11,515	$ 13,833
Cash dividends declared			(8,197)
Amortization of stock based compensation			1,497
Other			(108)
Balance at September 30, 2015	$ 268,137		268,137
2011 LTIP [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock repurchase			(3,825)
Other Repurchase Plan [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock repurchase			$ (11,804)