Summary of Significant Accounting Policies and Other Information - Narrative (Details)			1 Months Ended	12 Months Ended
	Jul. 14, 2021 USD ($)	Mar. 26, 2021 USD ($) day	Mar. 31, 2017 USD ($)	Dec. 31, 2021 USD ($) segment boardMember	Dec. 31, 2020 USD ($)	Mar. 25, 2022 USD ($) agreement	Mar. 24, 2022 USD ($)	Dec. 10, 2021 USD ($)	Nov. 09, 2021 USD ($)
Concentration Risk [Line Items]
Number of board members | boardMember				4
Short-term financing				$ 155,000,000	$ 130,000,000
Debt, long-term and short-term, combined amount				180,900,000
Cash and cash equivalents				$ 6,255,000	20,968,000
Number of operating segments | segment				1
Outstanding letters of credit amount				$ 2,100,000	2,300,000
Restricted cash				3,477,000	3,299,000
Research and development, excluding engineering expenses				21,400,000	24,300,000
Impairment losses				0	0
Product warranty reimbursements				4,500,000
Revolving credit facility
Concentration Risk [Line Items]
Short-term financing				$ 130,000,000	130,000,000
Subsequent Event
Concentration Risk [Line Items]
Debt instrument, number of loan agreements amended | agreement						2
Debt instrument, number of loan agreements | agreement						3
Minimum
Concentration Risk [Line Items]
Amortization period				3 years
Maximum
Concentration Risk [Line Items]
Amortization period				15 years
Share Purchase Agreement, Weichai Transaction
Concentration Risk [Line Items]
Consideration received on transaction			$ 60,000,000.0
Amended and Restated Credit Agreement, Standard Chartered | Revolving credit facility
Concentration Risk [Line Items]
Short-term financing				$ 130,000,000.0
Amended and Restated Credit Agreement, Standard Chartered | Revolving credit facility
Concentration Risk [Line Items]
Maximum borrowing capacity		$ 130,000,000
Number of days to submit borrowing request | day		5
Short-term financing				130,000,000
Lender fees									$ 600,000
Amended and Restated Credit Agreement, Standard Chartered | Revolving credit facility | LIBOR
Concentration Risk [Line Items]
Basis spread on variable rate		2.70%
Amended and Restated Credit Agreement, Standard Chartered | Revolving credit facility | Subsequent Event
Concentration Risk [Line Items]
Maximum borrowing capacity						$ 130,000,000
Lender fees						0
First Shareholder's Loan Agreement, Weichai | Revolving credit facility
Concentration Risk [Line Items]
Short-term financing				$ 0
First Shareholder's Loan Agreement, Weichai | LIBOR | Revolving credit facility
Concentration Risk [Line Items]
Basis spread on variable rate				4.50%
First Shareholder's Loan Agreement, Weichai | Subsequent Event | Revolving credit facility
Concentration Risk [Line Items]
Short-term financing							$ 0
First Shareholder's Loan Agreement, Weichai | Revolving credit facility
Concentration Risk [Line Items]
Maximum borrowing capacity		$ 130,000,000			$ 130,000,000
First Shareholder's Loan Agreement, Weichai | Revolving credit facility | Subsequent Event
Concentration Risk [Line Items]
Maximum borrowing capacity						130,000,000
Second Shareholder's Loan Agreement, Weichai | Revolving credit facility
Concentration Risk [Line Items]
Short-term financing				$ 25,000,000.0
Second Shareholder's Loan Agreement, Weichai | Subsequent Event | Revolving credit facility
Concentration Risk [Line Items]
Short-term financing							25,000,000
Second Shareholder's Loan Agreement, Weichai | Revolving credit facility
Concentration Risk [Line Items]
Maximum borrowing capacity	$ 25,000,000
Short-term financing				25,000,000
Lender fees									$ 600,000
Second Shareholder's Loan Agreement, Weichai | Revolving credit facility | LIBOR
Concentration Risk [Line Items]
Basis spread on variable rate	4.50%
Second Shareholder's Loan Agreement, Weichai | Revolving credit facility | Subsequent Event
Concentration Risk [Line Items]
Maximum borrowing capacity						25,000,000
Third Shareholder's Loan Agreement, Weichai | Revolving credit facility
Concentration Risk [Line Items]
Maximum borrowing capacity								$ 50,000,000
Short-term financing				$ 25,000,000
Third Shareholder's Loan Agreement, Weichai | Revolving credit facility | Subsequent Event
Concentration Risk [Line Items]
Short-term financing							35,700,000
Second Amended and Restated Credit Agreement, Standard Chartered | Subsequent Event | Revolving credit facility
Concentration Risk [Line Items]
Short-term financing							$ 130,000,000.0
Second Amended and Restated Credit Agreement, Standard Chartered | Revolving credit facility | Subsequent Event
Concentration Risk [Line Items]
Maximum borrowing capacity						130,000,000
Lender fees						$ 0