Stockholders' Equity - Changes in Stockholders' Equity (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Equity [Abstract]
Beginning Balance			$ 269,950
Net income for the nine months ended September 30, 2014	4,652	5,762	13,833	19,515
Cash dividends declared			(8,283)
Amortization of stock based compensation			2,816
Issued, purchased, retired common stock, and other			(34)
Ending Balance	$ 278,282		$ 278,282