Fair Value Measurements - Financial Assets and Liabilities Measured on a Recurring Basis at Fair Value (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Mutual fund assets	$ 26,448	$ 25,082
Derivative assets:
Foreign currency contracts	345	185
Total assets at fair value	26,793	25,267
Derivative liabilities:
Foreign currency contracts	29	10
Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Mutual fund assets	26,448	25,082
Derivative assets:
Total assets at fair value	26,448	25,082
Level 2 [Member]
Derivative assets:
Foreign currency contracts	345	185
Total assets at fair value	345	185
Derivative liabilities:
Foreign currency contracts	$ 29	$ 10