Basis of Presentation - Change in Accounting Policy - Balance Sheet (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Jan. 01, 2016
Accounting Changes
Contract assets	$ 1,984	$ 160
Deferred cost of sales	1,080	15,994
Deferred taxes	3,281	3,047
Accrued expenses and other current liabilities	54,297	58,068
Customer deposits and deferred revenue	94,473	112,032
Additional paid-in capital	1,054,331	1,051,953
Accumulated deficit	$ (228,697)	(212,870)
Accounting Standards Update 2014-09-09, Revenue from Contracts with Customers | Previously Reported
Accounting Changes
Deferred cost of sales		16,060
Deferred taxes		2,953
Accrued expenses and other current liabilities		60,339
Customer deposits and deferred revenue		108,953
Additional paid-in capital		1,053,079
Accumulated deficit		(213,376)
Accounting Standards Update 2014-09-09, Revenue from Contracts with Customers | Adjustments for adoption of guidance
Accounting Changes
Contract assets		160
Deferred cost of sales		(66)
Deferred taxes		94
Accrued expenses and other current liabilities		(2,271)
Customer deposits and deferred revenue		3,079
Additional paid-in capital		(1,126)
Accumulated deficit		$ 506	$ 6,900