Stockholders' Equity - Changes in Stockholders' Equity (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Equity [Abstract]
Beginning Balance			$ 251,419
Net income for the six months ended June 30, 2013	5,762	8,048	19,515	24,957
Cash dividends declared			(8,323)
Amortization of stock based compensation			2,200
Issued, purchased, retired common stock, and other			(972)
Ending Balance	$ 263,839		$ 263,839