Fair Value of Financial Instruments Fair Value of Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Total long-term debt	$ 3,852,019	$ 2,934,131
Total long-term debt, fair value	$ 3,810,981	$ 2,994,935