Revenue from Contract with Customers - Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
Sep. 30, 2019	Mar. 31, 2020	Dec. 31, 2019
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Unbilled receivable		$ 19,548	$ 20,482
Contract with Customer, Liability, Revenue Recognized	$ 7,600
ASUS
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Unbilled receivable		10,259	10,467
Receivable from the U.S. government		63,619	64,819
Contract assets		19,843	15,631
Contract liabilities		$ 10,675	$ 11,167

Amount, after 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.

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

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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 amount of receivables that are derived from government contracts.

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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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Unbilled amounts due for services rendered or to be rendered, actions taken or to be taken, or a promise to refrain from taking certain actions in accordance with the terms of a legally binding agreement between the entity and, at a minimum, one other party. An example would be amounts associated with contracts or programs where the recognized revenue for performance thereunder exceeds the amounts billed under the terms thereof as of the date of the balance sheet.

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