Fair Value Measurements - Financial Assets and Liabilities Measured at Fair Value Based on Three-Tier Fair Value Hierarchy (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value	$ 0	$ 0	$ 0
Total liabilities measured and recorded at fair value	0	0	$ 0
French Voluntary Departure Plan [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Postemployment Benefits Liability	$ 6,100	$ 5,300