Revenue Recognition - Contract with Customer, Contract Asset, Contract Liability, and Receivable (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Revenue Recognition and Deferred Revenue [Abstract]
Billed accounts receivable	$ 10,158		$ 10,158		$ 12,060
Unbilled receivables	39,717		39,717		19,161
Allowance for doubtful accounts	(116)		(116)		(308)
Accounts receivable – net	49,759		49,759		30,913
Contract liabilities	7,232		7,232		5,654
Significant changes in the contract liabilities balance (in thousands):
Revenue recognized that was included in the opening contract liability balance	823	$ 1,690	4,065	$ 5,208
Remaining performance obligations (funded backlog)	$ 163,351		$ 163,351		$ 127,735

Accounts Receivable And Contract With Customer, Asset, Allowance For Credit Loss, Current

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Amount, before allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.

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Amount, before allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time, classified as current.

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Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable, classified as current.

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Amount of revenue recognized that was previously included in balance of obligation to transfer good or service to customer for which consideration from customer has been received or is due.

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The total amount due to the entity within one year of the balance sheet date (or one operating cycle, if longer) from outside sources, including trade accounts receivable, notes and loans receivable, as well as any other types of receivables, net of allowances established for the purpose of reducing such receivables to an amount that approximates their net realizable value.

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Amount of transaction price allocated to performance obligation that has not been recognized as revenue.

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