Stock Repurchase Program - Additional Information (Detail) (USD $) Share data in Thousands, unless otherwise specified	1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2013	Dec. 31, 2007	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2008
Changes In Equity And Comprehensive Income Line Items [Line Items]
Stock repurchase program expiration date					Sep. 19, 2014
Stock repurchase program	$ 23,100,000	$ 5,000,000			$ 10,000,000		$ 16,100,000
Additional authorized amount stock repurchase program	7,000,000		7,000,000		7,000,000
Repurchase of common stock				380	365	568
Aggregate purchase price common stock Shares			$ 0	$ 1,500,000	$ 1,513,000	$ 2,164,000
Prior Stock Repurchase Program [Member]
Changes In Equity And Comprehensive Income Line Items [Line Items]
Stock repurchase program expiration date					Sep. 20, 2013