Stockholders' Equity - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended	12 Months Ended			57 Months Ended			12 Months Ended	1 Months Ended
	Feb. 27, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012	Dec. 31, 2008	Nov. 30, 2006	Dec. 31, 2012 Scenario, Forecast [Member]	Nov. 30, 2006 Sold Warrants
Sold warrants to acquire shares of our common stock									215
Sold warrants to acquire shares of our common stock, exercise price per share							19.55
Common stock excluded from calculation of diluted earnings per share		4.1	13.3	54.5
Number of shares authorized for issuance						250.0
Total Repurchases of Common Stock, shares		27.1			222.9
Total Repurchases of Common Stock		$ 700.0			$ 4,400.0
Common stock, shares reserved for future issuance		27.1			27.1
Plan to spend for the year on common stock repurchases								$ 1,000.0
Additional number of shares authorized for issuance	250.0