Accounts Receivable - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Taxi commission revenue receivables		$ 1,300
Changes in the allowance for doubtful accounts	$ 0	350
Accounts receivable	1,609	1,607	$ 1,219
Guizhou Qianxi Green Environmentally Friendly Taxi Service Co
Accounts, Notes, Loans and Financing Receivable [Line Items]
Changes in the allowance for doubtful accounts	$ 0
Accounts receivable		$ 400