Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Operating activities:
Net loss attributable to NextDecade Corporation	$ (21,990)	$ (30,362)
Adjustment to reconcile net loss to net cash used in operating activities
Depreciation	164	127
Share-based compensation expense	(12,537)	12,731
(Gain) loss on common stock warrant liabilities	965	(83)
(Gain) loss on investment securities	(276)	28
Realized gain on investment securities	(39)
Amortization of right-of-use asset	673
Changes in operating assets and liabilities:
Prepaid expenses	323	295
Accounts payable	84	(42)
Operating lease liabilities	(803)
Accrued expenses and other liabilities	153	4,660
Net cash used in operating activities	(33,283)	(12,646)
Investing activities:
Acquisition of property, plant and equipment	(18,609)	(11,460)
Proceeds from sale of investment securities	48,500
Purchase of investment securities	(16,106)	(55,100)
Net cash provided by (used in) investing activities	13,785	(66,560)
Financing activities:
Proceeds from equity issuance	20,945	79,055
Preferred stock dividends	(30)
Equity issuance costs	(95)	(1,653)
Shares repurchased related to share-based compensation	(650)	(19)
Net cash provided by financing activities	20,170	77,383
Net increase (decrease) in cash and cash equivalents	672	(1,823)
Cash and cash equivalents – beginning of period	3,169	35,703
Cash and cash equivalents – end of period	3,841	33,880
Non-cash investing activities:
Accounts payable for acquisition of property, plant and equipment	964	656
Accrued liabilities for acquisition of property, plant and equipment	15,316	6,056
Non-cash financing activities:
Accounts payable for equity issuance costs		150
Accrued liabilities for equity issuance costs	103	301
Paid-in-kind dividends on Series A and Series B Convertible Preferred Stock	7,791
Accretion of deemed dividends on Series A Convertible Preferred Stock	$ 1,324	$ 271