CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities:
Net loss	$ (257,680)	$ (216,807)
Adjustments to reconcile net loss to net cash used in operating activities:
Changes in fair value of warrant liabilities	0	47,808
Depreciation and amortization	2,831	1,261
Loss on disposal of property and equipment	1,003	0
Interest on non-recourse debt	30,022	29,545
Amortization of deferred revenue	0	(81)
Amortization of bond premiums	0	39
Amortization of debt issuance costs	38	109
Amortization of deferred rent	0	327
Right-of-use asset amortization	196	0
Decrease in allowance for doubtful accounts	0	(13)
Non-cash expense related to stock-based compensation	7,327	4,416
Changes in deferred revenue	65,000	0
Changes in other operating assets and liabilities	21,485	14,097
Net cash used in operating activities	(129,778)	(119,299)
Cash flows from investing activities
Purchases of marketable securities	0	(135)
Proceeds from sales/maturities of marketable securities	0	73,968
Purchases of property and equipment	(6,514)	(11,169)
Net cash (used in) provided by investing activities	(6,514)	62,664
Cash flows from financing activities:
Exercise of stock options, net	2,281	1,726
Exercise of warrants	0	28,125
Proceeds from the issuance of common stock in at-the-market offering	5,829	0
Proceeds from the issuance of non-recourse debt	0	182,216
Debt conversion fees	0	(3)
Tax withholding payments for stock-based compensation	0	(1,668)
Net cash provided by financing activities	8,110	577,647
Effect of changes in exchange rates on cash, cash equivalents and restricted cash	(24)	(65)
Net (decrease) increase in cash, cash equivalents and restricted cash	(128,206)	520,947
Cash, cash equivalents and restricted cash beginning of period	494,173	60,960
Cash, cash equivalents and restricted cash end of period	365,967	581,907
Supplemental disclosure of cash flow information:
Interest paid	338	950
Schedule for non-cash investing and financing activities:
Non-cash component of warrant exercise	0	139,755
Accrued capital expenditures	0	2,449
Shares received in cashless exercise	1,271	634
Total cash, cash equivalents and restricted cash	494,173	60,960
Private placement
Cash flows from financing activities:
Proceeds from private offering of common stock	0	67,784
Public offering
Cash flows from financing activities:
Proceeds from private offering of common stock	$ 0	$ 299,467