Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Assets:
Net Amount Presented in the Balance Sheets	$ 3,653
Liabilities:
Total liabilities	(30,952)
Recurring
Assets:
Derivative instruments	3,653	$ 56,963
Net Amount Presented in the Balance Sheets	3,653
Liabilities:
Derivative instruments	(24,909)	(459)
Noncurrent derivative instruments	(6,043)
Total liabilities	(30,952)
Net derivative asset (liability)	(27,299)	56,504
Recurring | Level 2
Assets:
Derivative instruments	4,094	69,864
Net Amount Presented in the Balance Sheets	4,094
Liabilities:
Derivative instruments	(21,782)	2,699
Noncurrent derivative instruments	(5,314)
Total liabilities	(27,096)
Net derivative asset (liability)	(23,002)	72,563
Recurring | Level 3
Assets:
Derivative instruments	(441)	(12,901)
Net Amount Presented in the Balance Sheets	(441)
Liabilities:
Derivative instruments	(3,127)	(3,158)
Noncurrent derivative instruments	(729)
Total liabilities	(3,856)
Net derivative asset (liability)	$ (4,297)	$ (16,059)