Fair Value of Financial Instruments Fair Value of Long-Term Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Total long-term debt	$ 3,990,308	$ 2,934,131
Total long-term debt, fair value	$ 4,050,447	$ 2,994,935