Debt - Narrative (Details)			3 Months Ended
	Mar. 22, 2024 USD ($) agreement	May 12, 2023 USD ($)	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Mar. 31, 2023 USD ($)	Dec. 10, 2021 USD ($)
Debt Instrument [Line Items]
Debt issuance costs			$ 100,000	$ 200,000
Short-term financing			139,820,000	144,820,000
Number of amended agreements | agreement	1
Number of agreements | agreement	4
Debt, long-term and short-term, combined amount			140,200,000	145,200,000
Cash and cash equivalents			33,063,000	22,758,000	$ 26,934,000
Accrued unpaid interest			2,300,000	1,900,000
$25 Million Loan Agreement | Secured Overnight Financing Rate (SOFR)
Debt Instrument [Line Items]
Basis spread on variable rate		4.05%
Revolving Credit Facility | Third Amended And Restated Credit Agreement
Debt Instrument [Line Items]
Debt issuance costs	$ 100,000
Paydown related to credit agreement			5,000,000.0
Proceeds related to credit agreement			0
Short-term financing			$ 45,000,000	50,000,000
Revolving Credit Facility | Third Amended And Restated Credit Agreement | Secured Overnight Financing Rate (SOFR)
Debt Instrument [Line Items]
Basis spread on variable rate	3.45%
Revolving Credit Facility | First Shareholder's Loan Agreement, Weichai
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 130,000,000.0
Revolving Credit Facility | First Shareholder's Loan Agreement, Weichai - Amendment
Debt Instrument [Line Items]
Maximum borrowing capacity	50,000,000
Revolving Credit Facility | $30 Million, $25 Million, and $50 Million Loan Agreements
Debt Instrument [Line Items]
Debt instrument, incremental borrowing cost			1.00%
Revolving Credit Facility | $30 Million Loan Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity			$ 30,000,000.0
Short-term financing			$ 19,820,000	19,820,000
Debt instrument, face amount	$ 30,000,000
Revolving Credit Facility | $30 Million Loan Agreement | Secured Overnight Financing Rate (SOFR)
Debt Instrument [Line Items]
Basis spread on variable rate			4.05%
Revolving Credit Facility | $25 Million Loan Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity			$ 25,000,000
Short-term financing			25,000,000	25,000,000
Debt instrument, face amount		$ 25,000,000
Revolving Credit Facility | $50 Million Loan Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity			50,000,000
Short-term financing			$ 50,000,000	$ 50,000,000
Debt instrument, face amount						$ 50,000,000
Revolving Credit Facility | $50 Million Loan Agreement | Secured Overnight Financing Rate (SOFR)
Debt Instrument [Line Items]
Basis spread on variable rate			4.65%