Debt and Credit Facilities - Total Debt Outstanding (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended																		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2013 5.25% Senior Notes due April 2023	Mar. 31, 2013 5.25% Senior Notes due April 2023	Dec. 31, 2012 5.25% Senior Notes due April 2023	Sep. 30, 2013 12% Senior Notes due February 2014	Dec. 31, 2012 12% Senior Notes due February 2014	Sep. 30, 2013 7.875% Senior Notes due June 2017	Dec. 31, 2012 7.875% Senior Notes due June 2017	Sep. 30, 2013 8.125% Senior Notes due September 2019	Dec. 31, 2012 8.125% Senior Notes due September 2019	Sep. 30, 2013 6.50% Senior Notes due December 2020	Dec. 31, 2012 6.50% Senior Notes due December 2020	Sep. 30, 2013 8.375% Senior Notes due September 2021	Dec. 31, 2012 8.375% Senior Notes due September 2021	Sep. 30, 2013 6.875% Senior Notes due July 2033	Dec. 31, 2012 6.875% Senior Notes due July 2033	Sep. 30, 2013 Term Loan A Facility	Sep. 30, 2013 Term Loan B Facility	Sep. 30, 2013 Term Loan A Facility due October 2016	Dec. 31, 2012 Term Loan A Facility due October 2016	Sep. 30, 2013 Term Loan B Facility due October 2018	Dec. 31, 2012 Term Loan B Facility due October 2018
Debt Instrument [Line Items]
Unamortized lender fees																					$ 11.0	$ 15.4	$ 9.4	$ 10.7
Unamortized discount									5.5								1.4	1.4					13.8	15.6
Debt interest rate				5.25%	5.25%	5.25%	12.00%	12.00%	7.875%	7.875%	8.125%	8.125%	6.50%	6.50%	8.375%	8.375%	6.875%	6.875%
Repurchase aggregate principal amount									400
Weighted average interest rate	6.20%		6.40%
Payments of long-term debt	$ 456.1	$ 88.6																	$ 51.0	$ 4.0