Long-Term Debt - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 13, 2012
Debt Instrument [Line Items]
Revolving credit facility	750
Revolving credit facility, interest rate, additional to LIBOR	2.00%
Revolving credit facility, interest rate, additional to Prime	1.00%
Revolving credit facility agreement	London interbank offered rate ("LIBOR") (as defined in the Revolving Credit Facility Agreement) plus 200 basis points or Prime (as defined in the Revolving Credit Facility Agreement) plus 100 basis points.
Revolving credit facility, average interest rate	2.47%
Outstanding letter of credit amount	8.9
Senior Unsecured Notes 5.25 Percent Due 2022
Debt Instrument [Line Items]
Senior notes, aggregate principal amount		500.0
Debt, interest rate	5.25%
Debt, due date	2022
Senior Unsecured Notes 6.875 Percent Due 2020
Debt Instrument [Line Items]
Senior notes, aggregate principal amount	650.0
Debt, interest rate	6.875%
Senior notes, net of original issue discount	644.8
Debt, due date	2020
Senior Unsecured Notes 8.5 Percent Due 2018
Debt Instrument [Line Items]
Senior notes, aggregate principal amount	600.0
Debt, interest rate	8.50%
Debt, due date	2018
Covenant Requirement | Minimum
Debt Instrument [Line Items]
Interest coverage ratio	2.25
Covenant Requirement | Maximum
Debt Instrument [Line Items]
Total leverage ratio	4.25