Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Operating activities:
Net loss attributable to NextDecade Corporation	$ (14,329)	$ (35,871)
Adjustment to reconcile net loss to net cash used in operating activities
Depreciation	196	251
Share-based compensation expense	(341)	(9,646)
(Gain) loss on Common Stock Warrant liabilities	(7,870)	2,657
Gain on investment securities	0	(100)
Realized loss (gain) on investment securities	423	(138)
Amortization of right-of-use assets	1,230	955
Amortization of other non-current assets	1,360	127
Prepaid expenses	191	573
Accounts payable	(370)	207
Operating lease liabilities	(874)	(1,624)
Accrued expenses and other liabilities	(5,869)	1,909
Net cash used in operating activities	(26,253)	(40,700)
Investing activities:
Acquisition of property, plant and equipment	(32,352)	(20,303)
Acquisition of other non-current assets	(10,911)	(6,875)
Proceeds from sale of investment securities	61,972	77,000
Purchase of investment securities	(188)	(66,515)
Net cash provided by (used in) investing activities	18,521	(16,693)
Financing activities:
Proceeds from sale of Rio Bravo Pipeline Company, LLC	15,000	0
Proceeds from equity issuance	0	70,945
Preferred stock dividends	(50)	(42)
Equity issuance costs	0	(293)
Shares repurchased related to share-based compensation	(346)	(650)
Net cash provided by financing activities	14,604	69,960
Net increase in cash and cash equivalents	6,872	12,567
Cash and cash equivalents – beginning of period	15,736	3,169
Cash and cash equivalents – end of period	22,608	15,736
Non-cash investing activities:
Accounts payable for acquisition of property, plant and equipment	16	11,351
Accrued liabilities for acquisition of property, plant and equipment	650	2,503
Pipeline assets obtained in exchange for other non-current liabilities	7,916	0
Common stock issued in lieu of cash	0	12,082
Non-cash financing activities:
Paid-in-kind dividends on Series A Convertible Preferred Stock	14,277	11,122
Accretion of deemed dividends on Series A Convertible Preferred Stock	$ 128	$ 1,517