Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Operating activities:
Net loss attributable to NextDecade Corporation	$ (12,050)	$ (21,990)
Adjustment to reconcile net loss to net cash used in operating activities
Depreciation	146	164
Share-based compensation expense (forfeiture)	(759)	(12,537)
(Gain) loss on common stock warrant liabilities	(6,147)	965
Gain on investment securities	0	(276)
Realized loss (gain) on investment securities	423	(39)
Amortization of right-of-use assets	984	673
Amortization of other non-current assets	1,042	0
Changes in operating assets and liabilities:
Prepaid expenses	61	323
Accounts payable	(478)	84
Operating lease liabilities	(710)	(803)
Accrued expenses and other liabilities	(5,258)	153
Net cash used in operating activities	(22,746)	(33,283)
Investing activities:
Acquisition of property, plant and equipment	(30,088)	(18,609)
Acquisition of other non-current assets	(9,390)	0
Proceeds from sale of investment securities	61,972	48,500
Purchase of investment securities	(188)	(16,106)
Net cash provided by investing activities	22,306	13,785
Financing activities:
Proceeds from sale of Rio Bravo	15,000	0
Proceeds from equity issuance	0	20,945
Preferred stock dividends	(41)	(30)
Equity issuance costs	0	(95)
Shares repurchased related to share-based compensation	(322)	(650)
Net cash provided by financing activities	14,637	20,170
Net increase in cash and cash equivalents	14,197	672
Cash and cash equivalents – beginning of period	15,736	3,169
Cash and cash equivalents – end of period	29,933	3,841
Non-cash investing activities:
Accounts payable for acquisition of property, plant and equipment	479	964
Accrued liabilities for acquisition of property, plant and equipment	382	15,316
Pipeline assets obtained in exchange for other non-current liabilities	6,670	0
Non-cash financing activities:
Accrued liabilities for equity issuance costs	0	103
Paid-in-kind dividends on Series A and Series B Convertible Preferred Stock	10,524	7,791
Accretion of deemed dividends on Series A Convertible Preferred Stock	$ 113	$ 1,324