Long-term Debt	3 Months Ended
Mar. 31, 2018
Debt Disclosure [Abstract]
Long-term Debt	Long-term Debt Credit facility. The Company's long-term debt consists of senior notes, a revolving corporate credit facility (the "Credit Facility") and the effects of issuance costs and discounts. The Credit Facility is maintained with a syndicate of financial institutions and has aggregate loan commitments of $1.5 billion that expire in August 2020. As of March 31, 2018, the Company had no outstanding borrowings under the Credit Facility and was in compliance with its debt covenants. Senior notes. The Company's 6.65% senior notes (the "6.65% Senior Notes") matured and were repaid in March 2017. The Company funded the $485 million repayment of the 6.65% Senior Notes with cash on hand. The Company's 6.875% senior notes (the "6.875% Senior Notes"), with an outstanding debt principal balance of $450 million, mature in May 2018 and are classified as current in the accompanying consolidated balance sheets as of March 31, 2018 and December 31, 2017. See Note 16 for additional information regarding the repayment of the Company's 6.875% Senior Notes in May 2018.

Long-term Debt

Credit facility. The Company's long-term debt consists of senior notes, a revolving corporate credit facility (the "Credit Facility") and the effects of issuance costs and discounts. The Credit Facility is maintained with a syndicate of financial institutions and has aggregate loan commitments of $1.5 billion that expire in August 2020. As of March 31, 2018, the Company had no outstanding borrowings under the Credit Facility and was in compliance with its debt covenants.

Senior notes. The Company's 6.65% senior notes (the "6.65% Senior Notes") matured and were repaid in March 2017. The Company funded the $485 million repayment of the 6.65% Senior Notes with cash on hand. The Company's 6.875% senior notes (the "6.875% Senior Notes"), with an outstanding debt principal balance of $450 million, mature in May 2018 and are classified as current in the accompanying consolidated balance sheets as of March 31, 2018 and December 31, 2017. See Note 16 for additional information regarding the repayment of the Company's 6.875% Senior Notes in May 2018.