Income Taxes - Narrative (Details) - USD ($)		3 Months Ended	12 Months Ended
		Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Loss Carryforwards [Line Items]
U.S. federal corporate tax rate				35.00%	35.00%	35.00%
Tax cuts and jobs act of 2017 incomplete accounting change in tax rate income tax expense		$ 8,000,000
Tax cuts and jobs act of 2017 incomplete accounting undistributed foreign E&P subject to the deemed mandatory repatriation and recognized				$ 174,000,000
Tax cuts and jobs act of 2017 incomplete accounting current income tax expense		8,100,000
Deferred Tax Assets, Gross		38,146,000		38,146,000	$ 58,316,000
Deferred Tax Assets, Tax Credit Carryforwards		6,654,000		6,654,000	11,380,000
Deferred Tax, Operating Loss Carryforwards		5,195,000		5,195,000	5,023,000
Valuation allowance		4,010,000		4,010,000	3,998,000
Decrease in tax expense	[1]			8,000,000
Liability for uncertain tax positions		1,700,000		1,700,000	2,700,000
Increase (Decrease) in Uncertain Tax Liability				100,000
Accrued Interest And Penalties Related To Continued Operations		100,000		100,000
Accrued Interest and Penalties for Discontinued Operations		400,000		400,000
Liabilities associated with discontinued operations uncertain tax positions		0		0	1,000,000
Income Taxes Paid				14,600,000	14,100,000	$ 10,100,000
Continuing Operations
Operating Loss Carryforwards [Line Items]
Expected tax position to be resolved or settled				1,300,000
Discontinued Operations
Operating Loss Carryforwards [Line Items]
Liability for uncertain tax positions		1,000,000		1,000,000
U.S
Operating Loss Carryforwards [Line Items]
Valuation allowance		4,000,000		4,000,000	4,000,000
Decrease in tax expense				600,000
U.S | Foreign Exchange
Operating Loss Carryforwards [Line Items]
Increase in foreign exchange				200,000
Foreign Tax Authority | German
Operating Loss Carryforwards [Line Items]
Valuation Allowance Operating Loss Carryforwards Change In Amount				(1,600,000)
State and Foreign
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards		68,400,000		68,400,000	63,000,000
Deferred Tax, Operating Loss Carryforwards		5,200,000		5,200,000	$ 5,000,000
State
Operating Loss Carryforwards [Line Items]
Increase in net operating loss				(500,000)
Foreign Income Tax Credit
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Tax Credit Carryforwards		400,000		400,000
Foreign Income Tax Credit | U.S
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Tax Credit Carryforwards		100,000		$ 100,000
Tax credit carryforward expiration period				10 years
Tax credit carryforward expiration year				2021
Foreign Income Tax Credit | Foreign Tax Authority | United Kingdom
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Tax Credit Carryforwards		300,000		$ 300,000
Valuation Allowance Operating Loss Carryforwards Change In Amount				300,000
Alternative Minimum Tax Credit Carryforward
Operating Loss Carryforwards [Line Items]
Tax credit carryforward		$ 6,200,000		$ 6,200,000
Scenario, Forecast
Operating Loss Carryforwards [Line Items]
U.S. federal corporate tax rate			21.00%

[1] Includes $0.6 million increase to the valuation allowance related to the remeasurement of deferred taxes due to the reduction in U.S. tax rate.