Stockholders' Investment - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	12 Months Ended
	Aug. 21, 2007	Dec. 31, 2008	Dec. 31, 2012	Dec. 31, 2011
Stockholders Equity Note [Line Items]
Common stock authorized shares			27,500,000
Common stock par value			$ 0.001	$ 0.001
Preferred stock authorized shares			5,000,000
Share repurchase plan additional authorized amount	$ 50.0
Purchase of additional common stock		588,408
Repurchase of common stock per share		$ 16.99
Total cost of repurchase of common stock		$ 10.0
Common stock held in treasury			6,200,000