Summary of Significant Accounting Policies - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Accounting Policies [Abstract]
Unsatisfied performance obligation	$ 60,200
Amount of remaining performance obligation	91.00%
Allowance for doubtful accounts	$ 4,815		$ 4,371
Unearned revenue	8,120		$ 11,459
Prior year unearned revenue recognized in period	2,700
Share-based compensation costs	$ 5,800	$ 3,400

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A valuation allowance for trade and other receivables due to an Entity within one year (or the normal operating cycle, whichever is longer) that are expected to be uncollectible.

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- Definition

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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- Definition

Total carrying amount of consideration received or receivable as of the balance sheet date on potential earnings that were not recognized as revenue or other forms of income in conformity with GAAP, and which are expected to be recognized as such within one year or the normal operating cycle, if longer.

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

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Percentage of remaining performance obligation to total remaining performance obligation not recognized as revenue.

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The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

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