Debt - (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Aug. 31, 2011
Long-term debt
Other	$ 6,508	$ 6,209
Long-term Debt	3,679,720	4,355,049
Less: Current portion	6,508	6,190
Less: deferred finance costs	(18,012)	(17,019)
Long-term debt	3,655,200	4,331,840
Maturity of primary debt
2016	348,000
2018	1,086,113
2019	339,607
2020	855,780
Thereafter	1,050,000
Total	3,679,500
2.35% senior notes due September 2016
Long-term debt
Senior Notes	$ 347,955	349,887
Interest rate on senior notes due (as a percent)	2.35%			2.35%
6.15% senior notes due February 2018
Long-term debt
Senior Notes	$ 921,162	930,693
Interest rate on senior notes due (as a percent)	6.15%
9.25% senior notes due January 2019
Long-term debt
Senior Notes	$ 339,607	339,607
Interest rate on senior notes due (as a percent)	9.25%		9.25%	9.25%
5.00% senior notes due September 2020
Long-term debt
Senior Notes	$ 683,839	698,253
Interest rate on senior notes due (as a percent)	5.00%
4.625% senior notes due September 2021
Long-term debt
Senior Notes	$ 698,628	698,388
Interest rate on senior notes due (as a percent)	4.625%				4.625%
5.10% senior notes due September 2023
Long-term debt
Senior Notes	$ 349,021	348,893
Interest rate on senior notes due (as a percent)	5.10%			5.10%
Term Loan Facility
Long-term debt
Senior Notes	$ 325,000
Revolving Credit Facility
Long-term debt
Revolving credit facility	0	450,000
Commercial paper
Long-term debt
Long-term Debt	$ 8,000	$ 533,119