Pension and Postretirement Benefits - Fair Value of the Plans' Assets by Asset Class (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Domestic Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value measurement domestic pension plans	$ 11,590	$ 10,416
Domestic Plans | Aggregate fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value measurement domestic pension plans	5,787	5,352
Domestic Plans | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value measurement domestic pension plans	5,390	4,580
Domestic Plans | Cash
Defined Benefit Plan Disclosure [Line Items]
Fair value measurement domestic pension plans	214	280
Domestic Plans | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value measurement domestic pension plans	199	204
Foreign Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value measurement domestic pension plans	9,493	10,576
Foreign Pension Plans | Aggregate fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value measurement domestic pension plans	4,414	4,082
Foreign Pension Plans | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value measurement domestic pension plans	4,889	4,518
Foreign Pension Plans | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value measurement domestic pension plans	190	1,976
Quoted Prices in Active Markets (Level 1) | Domestic Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value measurement domestic pension plans	11,391	10,212
Quoted Prices in Active Markets (Level 1) | Domestic Plans | Aggregate fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value measurement domestic pension plans	5,787	5,352
Quoted Prices in Active Markets (Level 1) | Domestic Plans | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value measurement domestic pension plans	5,390	4,580
Quoted Prices in Active Markets (Level 1) | Domestic Plans | Cash
Defined Benefit Plan Disclosure [Line Items]
Fair value measurement domestic pension plans	214	280
Quoted Prices in Active Markets (Level 1) | Foreign Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value measurement domestic pension plans	9,070	10,188
Quoted Prices in Active Markets (Level 1) | Foreign Pension Plans | Aggregate fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value measurement domestic pension plans	4,414	4,082
Quoted Prices in Active Markets (Level 1) | Foreign Pension Plans | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value measurement domestic pension plans	4,466	4,130
Quoted Prices in Active Markets (Level 1) | Foreign Pension Plans | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value measurement domestic pension plans	190	1,976
Significant Other Observable Inputs (Level 2) | Domestic Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value measurement domestic pension plans	199	204
Significant Other Observable Inputs (Level 2) | Domestic Plans | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value measurement domestic pension plans	199	204
Significant Other Observable Inputs (Level 2) | Foreign Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value measurement domestic pension plans	423	388
Significant Other Observable Inputs (Level 2) | Foreign Pension Plans | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value measurement domestic pension plans	$ 423	$ 388