Fair Value Measurements (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financial assets
Derivative asset - current	$ 6,605	$ 43,888
Derivative asset - noncurrent	6,300	21,121
Financial liabilities
Derivative liability - current	2,204	528
Derivative liability - noncurrent	1,367	1,891
Fair Value on a Recurring Basis
Financial assets
Derivative asset - current	6,605	43,888
Derivative asset - noncurrent	6,300	21,121
Total financial assets	12,905	65,009
Financial liabilities
Derivative liability - current	2,204	528
Derivative liability - noncurrent	1,367	1,891
Total financial liabilities	3,571	2,419
Level 1 \| Fair Value on a Recurring Basis
Financial assets
Derivative asset - current	0	0
Derivative asset - noncurrent	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	6,605	43,888
Derivative asset - noncurrent	6,300	21,121
Total financial assets	12,905	65,009
Financial liabilities
Derivative liability - current	2,204	528
Derivative liability - noncurrent	1,367	1,891
Total financial liabilities	3,571	2,419
Level 3 \| Fair Value on a Recurring Basis
Financial assets
Derivative asset - current	0	0
Derivative asset - noncurrent	0
Total financial assets	0	0
Financial liabilities
Derivative liability - current	0	0
Derivative liability - noncurrent	0	0
Total financial liabilities	$ 0	$ 0

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