Organization and Principal Activities - Narrative (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($) segment businessUnit	Dec. 31, 2022 USD ($)
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of operating segments | segment		1
Number of business units | businessUnit		2
Cash and cash equivalents		$ 1,249	$ 2,914
Accounts payable and accrued expenses		64,300
Current contingent consideration		727	867
Current portion of operating lease liabilities		3,222	2,031
Payments of short-term and long-term debt		24,500
Net loss		204,850	213,633
Accumulated deficit		(1,090,579)	(866,418)
Italy
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Cash and cash equivalents		1,200
Nonrelated Party
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Other current liabilities		$ 13,181	$ 9,287
Standby Equity Purchase Agreement
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Proceeds from sale of preferred shares, issuance of a convertible note and sale of financial assets	$ 30,000