Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Assets:
Noncurrent derivative instruments	$ 148	$ 0
Total assets	18,958
Liabilities:
Total liabilities	(5,741)
Recurring
Assets:
Derivative instruments	18,810	56,963
Noncurrent derivative instruments	148
Total assets	18,958
Liabilities:
Derivative instruments	(5,468)	(459)
Noncurrent derivative instruments	(273)
Total liabilities	(5,741)
Net derivative asset (liability)	13,217	56,504
Recurring | Level 2
Assets:
Derivative instruments	21,585	69,864
Noncurrent derivative instruments	148
Total assets	21,733
Liabilities:
Derivative instruments	(89)	2,699
Noncurrent derivative instruments	(273)
Total liabilities	(362)
Net derivative asset (liability)	21,371	72,563
Recurring | Level 3
Assets:
Derivative instruments	(2,775)	(12,901)
Noncurrent derivative instruments	0
Total assets	(2,775)
Liabilities:
Derivative instruments	(5,379)	(3,158)
Noncurrent derivative instruments	0
Total liabilities	(5,379)
Net derivative asset (liability)	$ (8,154)	$ (16,059)