Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Operating activities:
Net loss attributable to NextDecade Corporation	$ (4,872)	$ (18,762)
Adjustment to reconcile net loss to net cash used in operating activities
Depreciation	80	85
Share-based compensation expense (forfeiture)	(1,596)	(7,817)
(Gain) loss on common stock warrant liabilities	(7,774)	1,838
Gain on investment securities	0	(280)
Realized loss (gain) on investment securities	423	(34)
Amortization of right-of-use assets	655	399
Amortization of other non-current assets	688	0
Changes in operating assets and liabilities:
Prepaid expenses	(17)	(342)
Accounts payable	(384)	546
Operating lease liabilities	(502)	(266)
Accrued expenses and other liabilities	(5,483)	(601)
Net cash used in operating activities	(18,782)	(25,234)
Investing activities:
Acquisition of property, plant and equipment	(28,163)	(14,077)
Acquisition of other non-current assets	(7,857)	0
Proceeds from sale of investment securities	61,972	36,000
Purchase of investment securities	(188)	(15,803)
Net cash provided by investing activities	25,764	6,120
Financing activities:
Proceeds from sale of Rio Bravo	15,000	0
Proceeds from equity issuance	0	20,945
Preferred stock dividends	(28)	(26)
Shares repurchased related to share-based compensation	(111)	(431)
Net cash provided by financing activities	14,861	20,488
Net increase in cash and cash equivalents	21,843	1,374
Cash and cash equivalents – beginning of period	15,736	3,169
Cash and cash equivalents – end of period	37,579	4,543
Non-cash investing activities:
Accounts payable for acquisition of property, plant and equipment	342	958
Accrued liabilities for acquisition of property, plant and equipment	529	1,058
Non-cash financing activities:
Paid-in-kind dividends on Series A and Series B Convertible Preferred Stock	6,924	4,952
Accretion of deemed dividends on Series A Convertible Preferred Stock	$ 97	$ 1,039