Summary of Significant Accounting Policies - Rollforward of Deferred Revenue (Details) - USD ($) $ in Thousands		6 Months Ended
	Jan. 01, 2018	Jun. 30, 2018
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Beginning Balance	$ (54,231)	$ (47,611)
Revenue recognized that was included in deferred revenue at the beginning of the period		29,546
Consideration received in advance of services performed net of revenue recognized in the current period		(31,747)
Other		1,180
Ending Balance	(47,611)	$ (48,632)
ASC 606
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Reclassification - Adoption of ASC 606	2,276
ASC 606 | Deferred Revenue
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Cumulative effect adjustments	$ 4,344