Long-term Debt - Summary of Long-term Debt (Details) (Senior Notes [Member], USD $)	1 Months Ended
	Feb. 28, 2015	Mar. 31, 2015		Dec. 31, 2014
Debt Instrument [Line Items]
Net proceeds	$ 1,482,400,000
Debt issuance costs, net	17,600,000	400,000
5.375% Senior Notes [Member]
Debt Instrument [Line Items]
Principal Amount at Par		500,000,000		500,000,000
Fair Value		510,000,000	[1]	520,000,000	[1]
Interest rate		5.375%		5.375%
5.750% Senior Notes [Member]
Debt Instrument [Line Items]
Principal Amount at Par		400,000,000		400,000,000
Fair Value		407,500,000	[1]	416,000,000	[1]
Interest rate		5.75%		5.75%
5.50% Senior Notes [Member]
Debt Instrument [Line Items]
Principal Amount at Par		700,000,000	[2]
Fair Value		715,800,000	[1],[2]	0	[1],[2]
Interest rate	5.50%	5.50%	[2]
5.875% Senior Notes [Member]
Debt Instrument [Line Items]
Principal Amount at Par		800,000,000	[2]
Fair Value		$ 821,000,000	[1],[2]	$ 0	[1],[2]
Interest rate	5.875%	5.875%	[2]

[1] Based on quoted market prices in less active markets

[2] The net proceeds to the Company for the 5.50% and 5.875% Senior Notes issued in the first quarter of 2015 were an aggregate $1,482.4 million. Debt issuance costs of $17.6 million (of which $0.4 million were unpaid as of March 31, 2015) were recorded in "Other non-current assets" on the Consolidated Balance Sheets and are amortized over the term of the notes as "Interest expense" on the Consolidated Statements of Operations.