Debt Credit Agreement (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended	12 Months Ended
	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Sep. 30, 2016	Apr. 13, 2016
Line of Credit Facility [Line Items]
Interest Expense, Adequate Protection Payments				$ 121.4
Proceeds from long-term debt			$ 511.4	1,458.4	$ 975.7	$ 1.1
Payments of Debt Restructuring Costs	$ 10.3	$ 26.4
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Exit facility, maximum borrowing capacity			1,650.0	1,650.0
Long-term Debt		$ 947.0	1,558.1	1,558.1	0.0
Letters of credit outstanding			611.0	611.0				$ 675.0
Investments and Other Noncurrent Assets			479.3	479.3
Term Loan Facility [Member]
Line of Credit Facility [Line Items]
Exit facility, maximum borrowing capacity			$ 950.0	$ 950.0
Stated interest rate - percentage			4.50%	4.50%
2013 Term Loan Facility [Member]
Line of Credit Facility [Line Items]
Exit facility, maximum borrowing capacity			$ 1,200.0	$ 1,200.0
Long-term Debt			1,154.5	1,154.5	1,156.3
6.00% Senior Notes due November 2018 [Member]
Line of Credit Facility [Line Items]
Long-term Debt			$ 1,509.9	$ 1,509.9	1,508.9
Stated interest rate - percentage			6.00%	6.00%
6.25% Senior Notes due November 2021 [Member]
Line of Credit Facility [Line Items]
Long-term Debt			$ 1,327.7	$ 1,327.7	1,327.0
Stated interest rate - percentage			6.25%	6.25%			6.25%
6.50% Senior Notes due September 2020 [Member]
Line of Credit Facility [Line Items]
Long-term Debt			$ 645.8	$ 645.8	645.5
Stated interest rate - percentage			6.50%	6.50%			6.50%
7.875% Senior Notes due November 2026 [Member]
Line of Credit Facility [Line Items]
Long-term Debt			$ 245.9	$ 245.9	$ 245.8
Stated interest rate - percentage			7.875%	7.875%			7.875%
Eurocurrency Rate [Member] | Term Loan Facility [Member]
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate				1.00%