Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Operating activities:
Net loss attributable to NextDecade Corporation	$ (41,960)	$ (35,326)
Adjustment to reconcile net loss to net cash used in operating activities
Depreciation	171	106
Share-based compensation expense	16,840	22,693
Gain on Common Stock Warrant liabilities	(164)
Loss on investment securities	114
Changes in operating assets and liabilities:
Prepaid expenses	440	(1,003)
Other current assets	349	349
Accounts payable	124	(137)
Accrued expenses and other liabilities	801	488
Net cash used in operating activities	(23,285)	(12,830)
Investing activities:
Acquisition of property, plant and equipment	(18,658)	(14,833)
Issuance of note receivable		(115)
Repayment of note receivable		115
Cash received in reverse recapitalization		26,774
Proceeds from sale of investment securities	17,113
Purchase of investment securities	(84,616)	(79)
Net cash (used in) provided by investing activities	(86,161)	11,862
Financing activities:
Proceeds from equity issuance	79,055	30,100
Equity issuance costs	(2,104)	(5,953)
Shares repurchased related to share-based compensation	(35)
Payment of convertible preferred stock cash dividends	(4)
Net cash provided by financing activities	76,912	24,147
Net (decrease) increase in cash and cash equivalents	(32,534)	23,179
Cash and cash equivalents – beginning of period	35,703	12,524
Cash and cash equivalents – end of period	3,169	35,703
Non-cash investing activities:
Accounts payable for acquisition of property, plant and equipment	367	498
Accrued liabilities for acquisition of property, plant and equipment	4,014	$ 3,317
Non-cash financing activities:
Paid-in-kind dividends on Series A Convertible Preferred Stock	720
Accretion of deemed dividends on Series A Convertible Preferred Stock	$ 822