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Research And Development Expense (Excluding Engineering)

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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Number of reporting units tested for impairment of goodwill. A reporting unit is an operating segment or one level below an operating segment.

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Amount of cash restricted as to withdrawal or usage, classified as current. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits.

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Summary of Significant Accounting Policies and Other Information - Narrative (Details)	1 Months Ended	12 Months Ended
	Mar. 31, 2017 USD ($)	Dec. 31, 2020 USD ($) segment boardMember reportingUnit	Dec. 31, 2019 USD ($) reportingUnit
Concentration Risk [Line Items]
Number of board members \| boardMember		4
Number of operating segments \| segment		1
Outstanding letters of credit amount		$ 2,300,000
Restricted cash		3,299,000	$ 0
Research and development and engineering expenses		$ 24,300,000	$ 23,300,000
Number of reporting units \| reportingUnit		1	2
Impairment losses			$ 0
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