Description of Business and Summary of Significant Accounting Policies Impact of Change in Accounting Policy (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Other current assets	$ 30,533	$ 33,532
Assets, Current	290,867	252,932
Deferred tax asset, net	48,489	43,529
Other assets	15,889	11,720
Assets	1,162,444	1,113,013
Deferred Revenue, Current	27,492	22,562
Liabilities, Current	158,675	146,932
Deferred Revenue, Noncurrent	8,822	1,423
Liabilities	621,517	579,254
Retained Earnings (Accumulated Deficit)	523,668	510,975
Accounting Standards Update 2014-09 Adjustments
Other current assets	(870)	898
Assets, Current	(870)	898
Deferred tax asset, net	(2,843)	2,843
Other assets	(1,392)	1,502
Assets	(5,105)	5,243
Deferred Revenue, Current	(4,787)	5,124
Liabilities, Current	(4,787)	5,124
Deferred Revenue, Noncurrent	(7,565)	8,921
Liabilities	(12,352)	14,045
Retained Earnings (Accumulated Deficit)	$ 7,247	(8,802)
Balances with Adoption of ASC 606
Other current assets		34,430
Assets, Current		253,830
Deferred tax asset, net		46,372
Other assets		13,222
Assets		1,118,256
Deferred Revenue, Current		27,686
Liabilities, Current		152,056
Deferred Revenue, Noncurrent		10,344
Liabilities		593,299
Retained Earnings (Accumulated Deficit)		$ 502,173