FAIR VALUE MEASUREMENTS (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Level 1
Financial assets:
Cash and cash equivalents, fair value disclosure	$ 1,179,297	$ 519,652
Restricted cash, fair value disclosure	1,860	12,788
Level 2
Financial assets:
Cash and cash equivalents, fair value disclosure	0	0
Restricted cash, fair value disclosure	0	0
Level 3
Financial assets:
Cash and cash equivalents, fair value disclosure	0	0
Restricted cash, fair value disclosure	0	0
Convertible Notes | Level 1
Financial liabilities:
Debt fair value	880,026
Convertible Notes | Level 2
Financial liabilities:
Debt fair value	0
Convertible Notes | Level 3
Financial liabilities:
Debt fair value	0
Offtake Advances | Level 1
Financial liabilities:
Debt fair value	0	0
Offtake Advances | Level 2
Financial liabilities:
Debt fair value	0	0
Offtake Advances | Level 3
Financial liabilities:
Debt fair value	16,501	68,151
Equipment notes | Level 1
Financial liabilities:
Debt fair value	0	0
Equipment notes | Level 2
Financial liabilities:
Debt fair value	9,737	2,077
Equipment notes | Level 3
Financial liabilities:
Debt fair value	0	0
Carrying Amount
Financial assets:
Cash and cash equivalents, fair value disclosure	1,179,297	519,652
Restricted cash, fair value disclosure	1,860	12,788
Carrying Amount | Convertible Notes
Financial liabilities:
Debt fair value	674,927
Carrying Amount | Offtake Advances
Financial liabilities:
Debt fair value	16,082	66,450
Carrying Amount | Equipment notes
Financial liabilities:
Debt fair value	9,661	2,102
Fair Value
Financial assets:
Cash and cash equivalents, fair value disclosure	1,179,297	519,652
Restricted cash, fair value disclosure	1,860	12,788
Fair Value | Convertible Notes
Financial liabilities:
Debt fair value	880,026
Fair Value | Offtake Advances
Financial liabilities:
Debt fair value	16,501	68,151
Fair Value | Equipment notes
Financial liabilities:
Debt fair value	$ 9,737	$ 2,077