Fair Value of Financial Instruments Fair Value of Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Total long-term debt, excluding debt issuance costs	$ 2,381,370	$ 3,834,217
Total long-term debt, fair value, excluding debt issuance costs	$ 2,472,813	$ 3,793,179