Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities:
Net loss	$ (61,038)	$ (173,872)
DD&A	719	139
Adjustments to reconcile net loss to net cash used in operating activities:
Goodwill impairment	0	77,592
Gain on Series A preferred stock exchange feature	0	(2,209)
Share-based compensation	2,368	17,951
Share-based payments	0	19,397
Impairment charge and loss on transfer of assets	1,809	0
Net changes in working capital (Note 10)	4,103	(11,089)
Net cash used in operating activities	(52,039)	(72,091)
Cash flows from investing activities:
Cash received in acquisition	0	56
Purchase of natural gas properties	(268)	0
Proceeds from sale of asset	167	0
Purchase of property, plant and equipment	(3,333)	(905)
Proceeds from sale of available-for-sale securities	0	266
Net cash used in investing activities	(3,434)	(583)
Cash flows from financing activities:
Proceeds from issuance of common stock	133,800	212,712
Tax payments for net share settlement of equity awards (Note 10)	(5,664)	0
Equity offering costs	(4,090)	(235)
Net cash provided by financing activities	124,046	212,477
Net increase in cash and cash equivalents	68,573	139,803
Cash and cash equivalents, beginning of period	128,273	21,398
Cash and cash equivalents, end of period	$ 196,846	$ 161,201