Fair Value Measurements (Hierarchy) (Details) $ in Thousands	Dec. 31, 2014 USD ($)
Fair value of assets and liabilities
Total derivative liability net fair value	$ (6,914)
Recurring
Fair value of assets and liabilities
Total derivative asset net fair value	191,800
Total derivative liability net fair value	(38,500)
Total	153,300
Recurring | Level 2
Fair value of assets and liabilities
Total derivative asset net fair value	191,800
Total derivative liability net fair value	(38,500)
Total	$ 153,300