Commitments - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Commitments And Contingencies Disclosure [Line Items]
Committed purchase obligations	$ 118,671
Contribution by employer for employee saving plan	20,713	$ 19,624	$ 19,600
Standby Letters of Credit
Commitments And Contingencies Disclosure [Line Items]
Contingently liable for letters of credit, amount	$ 71,937