Debt - Additional Information (Detail) (USD $)				9 Months Ended				1 Months Ended
	Sep. 30, 2012 Senior Secured Credit Facility	Sep. 30, 2012 Senior Secured Term Loan A Facility	Sep. 30, 2012 Senior Secured Term Loan B Facility	Sep. 30, 2012 Senior Subordinated Convertible Notes	Sep. 30, 2012 Libor Plus Senior Secured Term Loan A Facility	Sep. 30, 2012 Libor Plus Senior Secured Term Loan B Facility	Feb. 29, 2012 Securitization Facility	Feb. 29, 2012 Amended Securitization Facility
Debt Instrument [Line Items]
Private offering senior subordinated convertible notes, aggregate principal amount				$ 500,000,000
Interest rate of debt instrument				1.875%
Debt instrument maturity year				2018
Net proceeds after deducting fees and expenses				487,000,000
Net proceeds from senior subordinated convertible notes used for repurchase of common stock				100,000,000
Conversion rate for common stock				14.115
Principal amount of convertible notes in to shares common stock				1,000
Convertible note, conversion price per share				$ 70.85
Convertible Notes, repurchase rate				100.00%
Percentage by which closing sale price is more than current conversion price to be convertible				130.00%
Number of trading days				20 days
Number of Consecutive trading days				30 days
Number Of Trading Days				60 days
Number of Consecutive trading days				10 days
Closing sale price of the common stock at the conversion				10.00%
Closing sale price of the common stock at the conversion				98.00%
Trading-day period				10 days
Debt conversion on or after the date				Jun. 01, 2018
Convertible Debt Initial Liability Component				418,000,000
Convertible Debt Equity Component				82,000,000
Effective interest rate				5.50%
Borrowing under the credit facility	$ 300,000,000	$ 150,000,000	$ 150,000,000				$ 300,000,000	$ 400,000,000
Debt instrument maturity year		2016-03	2017-01					2015-02
Basis spread on variable rate					2.25%	3.00%		0.90%
Unused line fee for securitization facility								0.45%