Changes in Stockholders' Equity (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Stockholders' Equity [Line Items]
Balance as of December 31, 2012	$ 153,409
Net income	16,290	17,807
Common stock issued from treasury stock	1,542
Excess tax benefits from share-based awards	315
Non-cash share-based compensation	2,249
Dividends declared	(2,676)
Other comprehensive income	446	715
Balance as of March 31, 2013	171,575
Common Stock
Stockholders' Equity [Line Items]
Balance as of December 31, 2012	16,169
Balance as of December 31, 2012, Shares	26,624
Common stock issued from treasury stock, shares	181
Balance as of March 31, 2013	16,169
Balance as of March 31, 2013, Shares	26,805
Treasury Stock
Stockholders' Equity [Line Items]
Balance as of December 31, 2012	(2,857)
Common stock issued from treasury stock	90
Balance as of March 31, 2013	(2,767)
Retained Earnings
Stockholders' Equity [Line Items]
Balance as of December 31, 2012	156,530
Net income	16,290
Common stock issued from treasury stock	1,452
Excess tax benefits from share-based awards	315
Non-cash share-based compensation	2,249
Dividends declared	(2,676)
Balance as of March 31, 2013	174,160
Accumulated Other Comprehensive Loss
Stockholders' Equity [Line Items]
Balance as of December 31, 2012	(16,433)
Other comprehensive income	446
Balance as of March 31, 2013	$ (15,987)