Fair Value Measurements (Carrying Values of Assets and Liabilities Not Required to Be Carried at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 08, 2016	Mar. 31, 2016
Senior Notes | 5.875% Senior Notes
Fair Value, Carrying Values and Fair Values of Assets and Liabilities Not Required to be Carried At Fair Value on a Recurring Basis [Line Items]
Coupon rate	5.875%
Convertible Senior Subordinated Notes | January 2012 Notes
Fair Value, Carrying Values and Fair Values of Assets and Liabilities Not Required to be Carried At Fair Value on a Recurring Basis [Line Items]
Coupon rate	4.00%
Convertible Senior Subordinated Notes | April 2013 Notes
Fair Value, Carrying Values and Fair Values of Assets and Liabilities Not Required to be Carried At Fair Value on a Recurring Basis [Line Items]
Coupon rate	1.25%
Senior Secured Second-Priority Notes | 5.25% Senior Notes
Fair Value, Carrying Values and Fair Values of Assets and Liabilities Not Required to be Carried At Fair Value on a Recurring Basis [Line Items]
Coupon rate	5.25%
Term Loan | Term Loan Due 2022
Fair Value, Carrying Values and Fair Values of Assets and Liabilities Not Required to be Carried At Fair Value on a Recurring Basis [Line Items]
Coupon rate		5.00%
Carrying Value
Assets:
Investment in Pop's Mandatorily Redeemable Preferred Stock Units	$ 96.8		$ 98.7
Liabilities:
Total liabilities, fair value disclosure	3,428.1		1,399.0
Carrying Value | Senior Notes | 5.875% Senior Notes
Liabilities:
Senior Notes, fair value disclosure	498.3		0.0
Carrying Value | Convertible Senior Subordinated Notes | January 2012 Notes
Liabilities:
Convertible notes, fair value disclosures	0.0		40.0
Carrying Value | Convertible Senior Subordinated Notes | April 2013 Notes
Liabilities:
Convertible notes, fair value disclosures	60.0		60.0
Carrying Value | Production Loans | Production Loans
Liabilities:
Loans, fair value disclosure	353.3		690.0
Carrying Value | Senior Secured Second-Priority Notes | 5.25% Senior Notes
Liabilities:
Senior Notes, fair value disclosure	0.0		220.8
Carrying Value | Term Loan | Term Loan A Facility
Liabilities:
Loans, fair value disclosure	961.8		0.0
Carrying Value | Term Loan | Term Loan B Facility
Liabilities:
Loans, fair value disclosure	1,554.7		0.0
Carrying Value | Term Loan | Term Loan Due 2022
Liabilities:
Loans, fair value disclosure	0.0		388.2
Fair Value | Fair Value (Level 3)
Assets:
Investment in Pop's Mandatorily Redeemable Preferred Stock Units	122.1		114.5
Fair Value | Fair Value (Level 2)
Liabilities:
Total liabilities, fair value disclosure	3,548.2		1,416.1
Fair Value | Fair Value (Level 2) | Senior Notes | 5.875% Senior Notes
Liabilities:
Senior Notes, fair value disclosure	542.1		0.0
Fair Value | Fair Value (Level 2) | Convertible Senior Subordinated Notes | January 2012 Notes
Liabilities:
Convertible notes, fair value disclosures	0.0		41.5
Fair Value | Fair Value (Level 2) | Convertible Senior Subordinated Notes | April 2013 Notes
Liabilities:
Convertible notes, fair value disclosures	58.5		54.2
Fair Value | Fair Value (Level 2) | Production Loans | Production Loans
Liabilities:
Loans, fair value disclosure	353.8		690.4
Fair Value | Fair Value (Level 2) | Senior Secured Second-Priority Notes | 5.25% Senior Notes
Liabilities:
Senior Notes, fair value disclosure	0.0		229.5
Fair Value | Fair Value (Level 2) | Term Loan | Term Loan A Facility
Liabilities:
Loans, fair value disclosure	983.8		0.0
Fair Value | Fair Value (Level 2) | Term Loan | Term Loan B Facility
Liabilities:
Loans, fair value disclosure	1,610.0		0.0
Fair Value | Fair Value (Level 2) | Term Loan | Term Loan Due 2022
Liabilities:
Loans, fair value disclosure	$ 0.0		$ 400.5