Debt (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Long-term debt
Other	$ 11,496	$ 437
Long-term Debt	4,082,636	4,379,700
Current portion of debt	11,445	364
Long-term debt	4,071,191	4,379,336
6.15% senior notes due February 2018
Long-term debt
Senior Notes	969,318	968,708
Interest rate on senior note due (as a percent)	6.15%
9.25% senior notes due January 2019
Long-term debt
Senior Notes	1,111,000	1,125,000
Interest rate on senior note due (as a percent)	9.25%
5.00% senior notes due September 2020
Long-term debt
Senior Notes	697,795	697,648
Interest rate on senior note due (as a percent)	5.00%
4.625% senior notes due September 2021
Long-term debt
Senior Notes	698,027	697,907
Interest rate on senior note due (as a percent)	4.625%
Revolving Credit Facility
Long-term debt
Revolving credit facility	300,000	890,000
Commercial paper
Long-term debt
Long-term Debt	$ 295,000