Summary of Significant Accounting Policies Cumulative Effect Adjustments (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Other Assets, Current	$ 29,783	$ 26,309	$ 11,620
Assets	632,856	598,794	587,204
Deferred Tax Assets, Net of Valuation Allowance, Noncurrent	32,320	32,303	35,402
Assets, Noncurrent	249,904	240,315	243,414
Assets, Current	382,952	358,479	343,790
Deferred Revenue	42,870	30,213	31,272
Other Liabilities, Current	35,127	44,041	40,346
Liabilities, Current	272,772	268,428	265,792
Liabilities	379,023	377,135	374,499
Retained Earnings (Accumulated Deficit)	44,854	14,327	(716)
Accumulated Other Comprehensive Income (Loss), Net of Tax	4,119	7,226	13,315
Stockholders' Equity Attributable to Parent	253,833	221,659	212,705
Liabilities and Equity	$ 632,856	598,794	$ 587,204
Accounting Standards Updated 2014-09 [Domain]
Other Assets, Current		14,689
Assets		11,590
Deferred Tax Assets, Net of Valuation Allowance, Noncurrent		(3,099)
Assets, Noncurrent		(3,099)
Assets, Current		14,689
Deferred Revenue		(1,059)
Other Liabilities, Current		3,695
Liabilities, Current		2,636
Liabilities		2,636
Retained Earnings (Accumulated Deficit)		8,954
Accumulated Other Comprehensive Income (Loss), Net of Tax		0
Stockholders' Equity Attributable to Parent		8,954
Liabilities and Equity		11,590
Accounting Standards Update 2016-01 [Member]
Other Assets, Current		0
Assets		0
Deferred Tax Assets, Net of Valuation Allowance, Noncurrent		0
Assets, Noncurrent		0
Assets, Current		0
Deferred Revenue		0
Other Liabilities, Current		0
Liabilities, Current		0
Liabilities		0
Retained Earnings (Accumulated Deficit)		6,089
Accumulated Other Comprehensive Income (Loss), Net of Tax		(6,089)
Stockholders' Equity Attributable to Parent		0
Liabilities and Equity		$ 0