Other Long-Term Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Other Long-Term Liabilities [Abstract]
Contract liabilities, net of current portion	$ 21,975	$ 21,033
Employee separation costs	7,477
Deferred rent and other facility costs	6,942	7,113
Deferred payments related to acquisitions	5,741	6,385
Loss on facilities not in use	4,121	5,652
Lease incentives	2,481	2,832
Other	1,386
Total other long-term liabilities	$ 50,123	$ 43,015