Fair Value Measurements (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Financial assets
Derivative asset - current	$ 0	$ 184
Financial liabilities
Derivative liability - current	14,803	11,805
Derivative liability - noncurrent	5,502	1,826
Fair Value on a Recurring Basis
Financial assets
Derivative asset - current	0	184
Derivative asset - noncurrent	0	0
Total financial assets	0	184
Financial liabilities
Derivative liability - current	14,803	11,805
Derivative liability - noncurrent	5,502	1,826
Total financial liabilities	20,305	13,631
Level 1 | Fair Value on a Recurring Basis
Financial assets
Derivative asset - current	0	0
Derivative asset - noncurrent	0	0
Total financial assets	0	0
Financial liabilities
Derivative liability - current	0	0
Derivative liability - noncurrent	0	0
Total financial liabilities	0	0
Level 2 | Fair Value on a Recurring Basis
Financial assets
Derivative asset - current	0	184
Derivative asset - noncurrent	0	0
Total financial assets	0	184
Financial liabilities
Derivative liability - current	14,803	11,805
Derivative liability - noncurrent	5,502	1,826
Total financial liabilities	20,305	13,631
Level 3 | Fair Value on a Recurring Basis
Financial assets
Derivative asset - current	0	0
Derivative asset - noncurrent	0	0
Total financial assets	0	0
Financial liabilities
Derivative liability - current	0	0
Derivative liability - noncurrent	0	0
Total financial liabilities	$ 0	$ 0