Long-Term Debt - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended					1 Months Ended		12 Months Ended					12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 London Interbank Offered Rate (LIBOR)	Dec. 31, 2013 Prime Rate	Mar. 13, 2012 Senior Unsecured Notes 5.25 Percent Due 2022	Jul. 31, 2012 Senior Unsecured Notes 4.9 percent	Dec. 31, 2012 Senior Unsecured Notes 8.5 Percent Due 2018	Dec. 31, 2013 Senior Unsecured Notes 5.25 Percent	Dec. 31, 2013 Senior Unsecured Notes 5.0 percent	Dec. 31, 2013 Senior Unsecured Notes 6.875 Percent Due 2020	Dec. 31, 2013 Covenant Requirement Minimum	Dec. 31, 2013 Covenant Requirement Maximum
Debt Instrument [Line Items]
Senior notes, aggregate principal amount						$ 500.0	$ 800.0		$ 1,300.0		$ 650.0
Debt, interest rate						5.25%	4.90%	8.50%	5.25%	5.00%	6.875%
Debt, due date						2022		2018			2020
Principal payments on long-term debt	0.3	600.5	0.5					600.0
Loss on extinguishment of debt		(82.1)						(82.1)
Senior notes, net of original issue discount or premiums	1,950.0								1,313.7		645.7
Revolving credit facility	950.0
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	2.25%
Outstanding letter of credit amount	6.1
Interest coverage ratio												200.00%
Total leverage ratio													425.00%
Long-term debt discount amount											4.3
Long -term debt premium amount									13.7
Interest expense	$ 123.3	$ 124.6	$ 105.5