Long-Term Debt (Details) $ in Thousands		1 Months Ended		3 Months Ended	5 Months Ended	6 Months Ended		12 Months Ended
	Mar. 20, 2014 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)	Nov. 30, 2014 USD ($)	Mar. 19, 2014 USD ($)
Long-Term Debt
Long-term debt, net of discounts		$ 4,540,663		$ 4,540,663	$ 4,540,663	$ 4,540,663		$ 3,621,404
Accrued interest payable		47,600		47,600	47,600	47,600
Deferred financing costs						20,270	$ 2,045
Pre-tax loss related to repurchase of Senior Notes				(117,860)		(117,860)
Non-cash write-off of the unamortized discount and deferred finance costs				14,700
Payment of redemption premiums and third-party expenses				103,200
Revolving credit facility
Long-Term Debt
Long-term debt, net of discounts		447,500		447,500	447,500	447,500		$ 97,600
Applicable interest rate (as a percent)								4.50%
Credit facility current lending capacity	$ 1,300,000
Extension of maturity	18 months
Accordion option to increase borrowing capacity under the Credit Facility	$ 500,000									$ 250,000
Deferred financing costs							$ 1,900
Letters of credit maximum borrowing capacity		150,000		150,000	150,000	150,000
Short-term swingline loan maximum borrowing capacity		10,000		10,000	$ 10,000	$ 10,000
Minimum Interest Coverage Ratio						2.5
Maximum leverage ratio prior to Collateral Release Date					5.5	5.25		5.5
Maximum leverage ratio after Collateral Release Date						5.00
Borrowings outstanding		447,500		447,500	$ 447,500	$ 447,500
Letters of credit outstanding amount		11,300		11,300	11,300	11,300
Unused borrowing capacity		841,200		841,200	841,200	$ 841,200
Revolving credit facility | Alternate Base Rate Loans | Minimum
Long-Term Debt
Margin prior to Collateral Release Date (as a percent)						0.50%
Margin after Collateral Release Date (as a percent)						0.125%
Revolving credit facility | Alternate Base Rate Loans | Maximum
Long-Term Debt
Margin prior to Collateral Release Date (as a percent)						1.50%
Margin after Collateral Release Date (as a percent)						1.00%
Revolving credit facility | Alternate Base Rate Loans | Prime rate
Long-Term Debt
Basis of variable interest rate						prime rate
Revolving credit facility | Alternate Base Rate Loans | Federal funds effective swap rate
Long-Term Debt
Basis of variable interest rate						Federal Funds Rate
Spread on variable rate basis (as a percent)						0.50%
Revolving credit facility | Alternate Base Rate Loans | One month LIBOR
Long-Term Debt
Basis of variable interest rate						One month LIBOR
Spread on variable rate basis (as a percent)						1.00%
Revolving credit facility | LIBO Rate Loans | Minimum
Long-Term Debt
Margin prior to Collateral Release Date (as a percent)						1.50%
Margin after Collateral Release Date (as a percent)						1.125%
Revolving credit facility | LIBO Rate Loans | Maximum
Long-Term Debt
Margin prior to Collateral Release Date (as a percent)						2.50%
Margin after Collateral Release Date (as a percent)						2.00%
Revolving credit facility | LIBO Rate Loans | One month LIBOR
Long-Term Debt
Basis of variable interest rate						LIBOR
Revolving credit facility | Credit facility bearing interest of 2.4 percent
Long-Term Debt
Long-term debt, net of discounts		$ 250,000		$ 250,000	$ 250,000	$ 250,000
Applicable interest rate (as a percent)		2.40%		2.40%	2.40%	2.40%
Revolving credit facility | Credit facility bearing interest of 4.5 percent
Long-Term Debt
Long-term debt, net of discounts		$ 197,500		$ 197,500	$ 197,500	$ 197,500
Applicable interest rate (as a percent)		4.50%		4.50%	4.50%	4.50%
Senior Notes
Long-Term Debt
Estimated aggregate fair value of debt		$ 4,058,000		$ 4,058,000	$ 4,058,000	$ 4,058,000		$ 3,563,000
Senior Notes | 2020 Senior Notes, 6.75% interest, issued November 2010 and due November 2020
Long-Term Debt
Long-term debt, net of discounts								$ 500,000
Debt instrument, stated interest rate percentage								6.75%
Amount of debt repurchased		500,000
Senior Notes | 2021 Senior Notes, 6.5% interest, issued February and March 2011 and due August 2021
Long-Term Debt
Long-term debt, net of discounts								$ 324,587
Debt instrument, stated interest rate percentage								6.50%
Long-term debt, discounts								$ 413
Amount of debt repurchased		325,000
Senior Notes | 2022 Senior Notes, 6.25% interest, issued October 2011 and due June 2022
Long-Term Debt
Long-term debt, net of discounts								$ 455,000
Debt instrument, stated interest rate percentage								6.25%
Amount of debt repurchased		455,000
Senior Notes | 2023A Senior Notes, 5.5% interest, issued August 2012 and due February 2023
Long-Term Debt
Long-term debt, net of discounts		$ 744,553		$ 744,553	$ 744,553	$ 744,553		$ 744,217
Debt instrument, stated interest rate percentage		5.50%		5.50%	5.50%	5.50%		5.50%
Long-term debt, discounts		$ 5,447		$ 5,447	$ 5,447	$ 5,447		$ 5,783
Senior Notes | 2023B Senior Notes, 4.5% interest, issued January 2013 and due July 2023
Long-Term Debt
Long-term debt, net of discounts		$ 1,000,000		$ 1,000,000	$ 1,000,000	$ 1,000,000		$ 1,000,000
Debt instrument, stated interest rate percentage		4.50%		4.50%	4.50%	4.50%		4.50%
Senior Notes | 2024 Senior Notes, 4.875% interest, issued November 2014 and March 2015, due December 2024
Long-Term Debt
Long-term debt, net of discounts		$ 1,160,204		$ 1,160,204	$ 1,160,204	$ 1,160,204		$ 500,000
Debt instrument, stated interest rate percentage		4.875%		4.875%	4.875%	4.875%		4.875%
Long-term debt, premium		$ 10,204		$ 10,204	$ 10,204	$ 10,204
Senior Notes | 2024 Senior Notes, 4.875% interest, issued March 2015 and due December 2024
Long-Term Debt
Debt instrument, stated interest rate percentage			4.875%
Aggregate principal amount			$ 650,000
Proceeds from issuance of senior notes, net of underwriting fees and the other expenses of the offering			653,600
Accrued interest on notes issued			$ 9,000
Senior Notes | 2024 Senior Notes, 4.875% interest, issued November 2014 and due December 2024
Long-Term Debt
Debt instrument, stated interest rate percentage									4.875%
Aggregate principal amount									$ 500,000
Senior Notes | 2025 Senior Notes, 4.875% interest, issued June 2015 and due June 2025
Long-Term Debt
Long-term debt, net of discounts		$ 1,188,406		$ 1,188,406	$ 1,188,406	$ 1,188,406
Debt instrument, stated interest rate percentage		4.875%		4.875%	4.875%	4.875%
Long-term debt, premium		$ 11,594		$ 11,594	$ 11,594	$ 11,594
Aggregate principal amount		1,200,000		$ 1,200,000	$ 1,200,000	$ 1,200,000
Proceeds from issuance of senior notes, net of underwriting fees and the other expenses of the offering		1,174,900
Accrued interest on notes issued		$ 23,000