Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Operating activities:
Net loss attributable to NextDecade Corporation	$ (35,871)	$ (41,960)
Adjustment to reconcile net loss to net cash used in operating activities
Depreciation	251	171
Share-based compensation expense	(9,646)	16,840
Loss (gain) on Common Stock Warrant liabilities	2,657	(164)
(Gain) loss on investment securities	(100)	114
Realized gain on investment securities	(138)
Amortization of right-of-use assets	955
Amortization of other non-current assets	127
Changes in operating assets and liabilities:
Prepaid expenses	573	440
Other current assets		349
Accounts payable	207	124
Operating lease liabilities	(1,624)
Accrued expenses and other liabilities	1,909	801
Net cash used in operating activities	(40,700)	(23,285)
Investing activities:
Acquisition of property, plant and equipment	(20,303)	(18,658)
Proceeds from sale of investment securities	77,000	17,113
Purchase of investment securities	(66,515)	(84,616)
Acquisition of other non-current assets	(6,875)
Net cash used in investing activities	(16,693)	(86,161)
Financing activities:
Proceeds from equity issuance	70,945	79,055
Preferred stock dividends	(42)	(4)
Equity issuance costs	(293)	(2,104)
Shares repurchased related to share-based compensation	(650)	(35)
Net cash provided by financing activities	69,960	76,912
Net increase (decrease) in cash and cash equivalents	12,567	(32,534)
Cash and cash equivalents – beginning of period	3,169	35,703
Cash and cash equivalents – end of period	15,736	3,169
Non-cash investing activities:
Accounts payable for acquisition of property, plant and equipment	11,351	367
Accrued liabilities for acquisition of property, plant and equipment	2,503	4,014
Common stock issued in lieu of cash	12,082
Non-cash financing activities:
Paid-in-kind dividends on Series A Convertible Preferred Stock	11,122	720
Accretion of deemed dividends on Series A Convertible Preferred Stock	$ 1,517	$ 822