Fair Value Measurements - Financial Assets and Liabilities Measured on a Recurring Basis at Fair Value (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Mutual fund assets	$ 25,615	$ 25,082
Derivative assets:
Foreign currency contracts	31	185
Total assets at fair value	25,646	25,267
Derivative liabilities:
Foreign currency contracts	61	10
Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Mutual fund assets	25,615	25,082
Derivative assets:
Total assets at fair value	25,615	25,082
Level 2 [Member]
Derivative assets:
Foreign currency contracts	31	185
Total assets at fair value	31	185
Derivative liabilities:
Foreign currency contracts	$ 61	$ 10