Significant Accounting Policies - Schedule of Cumulative Impact of Adoption of ASC 842 Using Retrospective Approach (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Significant Accounting Policies [Line Items]
Long-term right-of-use assets	$ 125,110
Total assets	1,873,226			$ 1,733,288
Lease liabilities (current)	11,489
Deferred gain on sale of liquids gathering system				94,636
Long-term lease liabilities	113,642
Total liabilities	2,729,451			2,781,910
Retained earnings (loss)	(2,995,490)			(3,186,016)
Total stockholders' equity (deficit)	(856,225)	$ (914,003)		(1,048,622)	$ (1,114,830)	$ (1,096,739)	$ (1,154,636)
Total liabilities and stockholders' equity (deficit)	$ 1,873,226			$ 1,733,288
ASC 842
Significant Accounting Policies [Line Items]
Long-term right-of-use assets			$ 130,649
Total assets			1,863,937
Lease liabilities (current)			11,141
Long-term lease liabilities			121,326
Total liabilities			2,819,741
Retained earnings (loss)			(3,093,198)
Total stockholders' equity (deficit)			(955,804)
Total liabilities and stockholders' equity (deficit)			1,863,937
ASC 842 | Impact of ASC 842
Significant Accounting Policies [Line Items]
Long-term right-of-use assets			130,649
Total assets			130,649
Lease liabilities (current)			11,141
Deferred gain on sale of liquids gathering system			(94,636)
Long-term lease liabilities			121,326
Total liabilities			37,831
Retained earnings (loss)			92,818
Total stockholders' equity (deficit)			92,818
Total liabilities and stockholders' equity (deficit)			$ 130,649