Senior Notes (Schedule of Senior Notes) (Details) (USD $)	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Carrying Value	$ 2,274,700,000		$ 850,800,000
Senior Notes [Member]
Debt Instrument [Line Items]
Face Value	705,000,000		405,000,000
Unamortized Net Premium/(Discount)	1,000,000		4,000,000
Carrying Value	706,000,000		409,000,000
Senior Notes [Member] | 7.75% Senior Notes Due 2042 [Member]
Debt Instrument [Line Items]
Interest Rate	7.75%
Face Value	55,000,000		55,000,000
Unamortized Net Premium/(Discount)	0		0
Carrying Value	55,000,000		55,000,000
Senior Notes [Member] | 5.875% Senior Notes Dues April 2024 [Member]
Debt Instrument [Line Items]
Interest Rate	5.875%	5.875%
Face Value	300,000,000	300,000,000	0
Unamortized Net Premium/(Discount)	(2,700,000)		0
Carrying Value	297,300,000		0
Senior Notes [Member] | 8.75% Senior Notes, Due 2019 [Member]
Debt Instrument [Line Items]
Interest Rate	8.75%
Face Value	350,000,000		350,000,000
Unamortized Net Premium/(Discount)	3,700,000		4,000,000
Carrying Value	$ 353,700,000		$ 354,000,000