Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Operating activities:
Net loss attributable to NextDecade Corporation	$ (18,762)	$ (19,682)
Adjustment to reconcile net loss to net cash used in operating activities
Depreciation	85	77
Share-based compensation expense	(7,817)	11,251
Loss on common stock warrant liabilities	1,838
(Gain) loss on investment securities	(280)	25
Realized gain on investment securities	(34)
Amortization of right-of-use asset	399
Changes in operating assets and liabilities:
Prepaid expenses	(342)	(96)
Accounts payable	546	(58)
Operating lease liabilities	(266)
Accrued expenses and other liabilities	(601)	(578)
Net cash used in operating activities	(25,234)	(9,061)
Investing activities:
Acquisition of property, plant and equipment	(14,077)	(7,746)
Proceeds from sale of investment securities	36,000
Purchase of investment securities	(15,803)	(50)
Net cash provided by (used in) investing activities	6,120	(7,796)
Financing activities:
Proceeds from equity issuance	20,945
Preferred stock dividends	(26)
Shares repurchased related to share-based compensation	(431)
Net cash provided by financing activities	20,488
Net increase (decrease) in cash and cash equivalents	1,374	(16,857)
Cash and cash equivalents – beginning of period	3,169	35,703
Cash and cash equivalents – end of period	4,543	18,846
Non-cash investing activities:
Accounts payable for acquisition of property, plant and equipment	958	453
Accrued liabilities for acquisition of property, plant and equipment	1,058	$ 6,930
Non-cash financing activities:
Paid-in-kind dividends on series A and series B convertible preferred stock	4,952
Accretion of deemed dividends on series A convertible preferred stock	$ 1,039