Company's Debt (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2011	Dec. 31, 2010
Notes 5 Point 5 Percent Due 2014
Debt Instrument [Line Items]
Original issue discount	$ 1.2	$ 1.3
Fair value adjustments for unrealized gains on derivative instruments	11.1	9.3
Debt, interest rate	5.50%	5.50%
Debt, due date	Due 2014	Due 2014
Notes 8 Point 875 Percent Due 2019
Debt Instrument [Line Items]
Original issue discount	3.1	3.3
Debt, interest rate	8.875%	8.875%
Debt, due date	Due 2019	Due 2019
Debentures 7 Point 25 Percent Due 2025
Debt Instrument [Line Items]
Debt, interest rate	7.25%	7.25%
Debt, due date	Due 2025	Due 2025
Debentures 6 Point 5 Percent Due 2034
Debt Instrument [Line Items]
Original issue discount	$ 4.5	$ 4.5
Debt, interest rate	6.50%	6.50%
Debt, due date	Due 2034	Due 2034