Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Assets:
Total assets	$ 3,235
Liabilities:
Total liabilities	(59,327)
Recurring
Assets:
Derivative instruments	3,235	$ 56,963
Total assets	3,235
Liabilities:
Derivative instruments	(46,452)	(459)
Noncurrent derivative instruments	(12,875)
Total liabilities	(59,327)
Net derivative asset (liability)	(56,092)	56,504
Recurring | Level 2
Assets:
Derivative instruments	4,705	69,864
Total assets	4,705
Liabilities:
Derivative instruments	(38,177)	2,699
Noncurrent derivative instruments	(11,970)
Total liabilities	(50,147)
Net derivative asset (liability)	(45,442)	72,563
Recurring | Level 3
Assets:
Derivative instruments	(1,470)	(12,901)
Total assets	(1,470)
Liabilities:
Derivative instruments	(8,275)	(3,158)
Noncurrent derivative instruments	(905)
Total liabilities	(9,180)
Net derivative asset (liability)	$ (10,650)	$ (16,059)