Revenue - Summary of Total Receivables (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Billed receivables	$ 187,080	$ 239,275
Allowance for doubtful accounts	(3,790)	(3,912)
Billed receivables, net	183,290	235,363
Accrued receivables	365,478	336,858
Significant financing component	(33,109)	(35,029)
Total accrued receivables, net	332,369	301,829
Less: current accrued receivables	152,668	123,053
Less: current significant financing component	(10,625)	(10,234)
Total long-term accrued receivables, net	190,326	189,010
Total receivables, net	$ 515,659	$ 537,192

The amount of unbilled contracts receivable due within one year or the normal operating cycle, if longer.

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- Definition

Amount received for services rendered and products shipped, but not yet billed, for non-contractual agreements net of the significant financing component.

+ References

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Amount, after accumulated amortization, of the significant financing component related to unbilled receivable balances.

+ References

No definition available.

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Amount, after accumulated amortization, of the significant financing component related to unbilled receivable balances due within one year of the balance sheet date.

+ References

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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, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business.

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

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Amount of allowance for credit loss on accounts receivable, classified as current.

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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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- Definition

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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