Summary of Assets and Liabilities Recorded at Fair Value on Recurring Basis (Detail) - Recurring - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Assets:
Assets, fair value	$ 268,098	$ 780,793
Liabilities:
Liabilities, fair value	46,495	42,044
Money Market Mutual Funds | Cash and Cash Equivalents
Assets:
Assets, fair value	61,000	37,100
Money Market Mutual Funds | Other Assets
Assets:
Assets, fair value	71,018	70,995
Certificates of Deposit | Other Assets
Assets:
Assets, fair value	2,200	2,300
Equity Securities | Other Assets
Assets:
Assets, fair value	86,539	78,367
Term Deposit | Cash and Cash Equivalents
Assets:
Assets, fair value		540,000
Deferred Compensation Assets | Other Assets
Assets:
Assets, fair value	46,495	42,044
Foreign Currency Foreign Exchange Contracts | Other Current Assets
Assets:
Assets, fair value	846	9,987
Deferred Compensation Liability | Other Noncurrent Liabilities
Liabilities:
Liabilities, fair value	46,495	42,044
Basis of Fair Value Measurement, Level 1
Assets:
Assets, fair value	265,052	228,506
Liabilities:
Liabilities, fair value	46,495	42,044
Basis of Fair Value Measurement, Level 1 | Money Market Mutual Funds | Cash and Cash Equivalents
Assets:
Assets, fair value	61,000	37,100
Basis of Fair Value Measurement, Level 1 | Money Market Mutual Funds | Other Assets
Assets:
Assets, fair value	71,018	70,995
Basis of Fair Value Measurement, Level 1 | Equity Securities | Other Assets
Assets:
Assets, fair value	86,539	78,367
Basis of Fair Value Measurement, Level 1 | Deferred Compensation Assets | Other Assets
Assets:
Assets, fair value	46,495	42,044
Basis of Fair Value Measurement, Level 1 | Deferred Compensation Liability | Other Noncurrent Liabilities
Liabilities:
Liabilities, fair value	46,495	42,044
Basis of Fair Value Measurement, Level 2
Assets:
Assets, fair value	3,046	552,287
Basis of Fair Value Measurement, Level 2 | Certificates of Deposit | Other Assets
Assets:
Assets, fair value	2,200	2,300
Basis of Fair Value Measurement, Level 2 | Term Deposit | Cash and Cash Equivalents
Assets:
Assets, fair value		540,000
Basis of Fair Value Measurement, Level 2 | Foreign Currency Foreign Exchange Contracts | Other Current Assets
Assets:
Assets, fair value	$ 846	$ 9,987