Fair Value Measurement - Financial Assets and Liabilities Accounted for at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments under executive deferred compensation plan	$ 25,678	$ 26,292
Private equity securities	30	26
Foreign currency forward contracts, assets	388	431
Obligations under executive deferred compensation plan	25,678	26,292
Quoted Prices in Active Markets for Identical Items (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments under executive deferred compensation plan	25,678	26,292
Private equity securities	30	26
Foreign currency forward contracts, assets	0	0
Obligations under executive deferred compensation plan	25,678	26,292
Quoted Prices in Active Markets for Similar Items (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments under executive deferred compensation plan	0	0
Private equity securities	0	0
Foreign currency forward contracts, assets	388	431
Obligations under executive deferred compensation plan	0	0
Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments under executive deferred compensation plan	0	0
Private equity securities	0	0
Foreign currency forward contracts, assets	0	0
Obligations under executive deferred compensation plan	0	0
Fair Value Measured at Net Asset Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Private equity securities	$ 7,165	$ 7,195