Long-Term Debt - Additional Information (Detail) (USD $)	9 Months Ended		9 Months Ended						3 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014 London Interbank Offered Rate (LIBOR)	Sep. 30, 2014 Prime Rate	Sep. 30, 2014 Revolving Credit Facility	Sep. 30, 2014 Revolving Credit Facility Amendment No.1	Sep. 30, 2014 Revolving Credit Facility Before Amendment	Sep. 30, 2014 Covenant Requirement Minimum	Sep. 30, 2014 Covenant Requirement Maximum	Sep. 30, 2014 Senior Unsecured Notes 5.25 Percent	Sep. 30, 2014 Senior Unsecured Notes 5.0 percent	Sep. 30, 2014 Senior Unsecured Notes 6.875 Percent Due 2020
Debt Instrument [Line Items]
Senior notes, aggregate principal amount										$ 1,300,000,000		$ 650,000,000
Debt, interest rate										5.25%	5.00%	6.875%
Senior notes, net of original issue discount or premiums										1,312,700,000		646,000,000
Debt, due date					2017							2020
Revolving credit facility						1,400,000,000	950,000,000
Borrowings on line of credit	668,000,000				668,000,000
Revolving credit facility, interest rate, additional rate			2.00%	1.00%
Revolving credit facility agreement	Borrowings under the Revolving Credit Facility bear interest at an annual rate equal to the London interbank offered rate ("LIBOR") (as defined in the Revolving Credit Facility) plus 200 basis points or Prime (as defined in the Revolving Credit Facility) plus 100 basis points.
Revolving credit facility, average interest rate	2.22%
Outstanding letter of credit amount	$ 6,900,000	$ 6,100,000
Interest coverage ratio								200.00%
Total leverage ratio									425.00%