Summary of Assets and Liabilities Recorded at Fair Value on Recurring Basis (Detail) - Recurring - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Assets:
Assets, fair value	$ 703,701	$ 178,706
Liabilities:
Liabilities, fair value	36,307	35,510
Term Deposit | Cash and Cash Equivalents
Assets:
Assets, fair value	540,000
Money Market Mutual Funds | Other Assets
Assets:
Assets, fair value	60,931	60,175
Certificates of Deposit | Other Assets
Assets:
Assets, fair value	2,200	2,200
Available for Sale Securities | Other Assets
Assets:
Assets, fair value	61,082	70,478
Deferred Compensation Assets | Other Assets
Assets:
Assets, fair value	36,307	35,510
Foreign Currency Foreign Exchange Contracts | Other Current Assets
Assets:
Assets, fair value	3,181	10,343
Deferred Compensation Liability | Other Noncurrent Liabilities
Liabilities:
Liabilities, fair value	36,307	35,510
Basis of Fair Value Measurement, Level 1
Assets:
Assets, fair value	160,520	168,363
Liabilities:
Liabilities, fair value	36,307	35,510
Basis of Fair Value Measurement, Level 1 | Money Market Mutual Funds | Other Assets
Assets:
Assets, fair value	60,931	60,175
Basis of Fair Value Measurement, Level 1 | Certificates of Deposit | Other Assets
Assets:
Assets, fair value	2,200	2,200
Basis of Fair Value Measurement, Level 1 | Available for Sale Securities | Other Assets
Assets:
Assets, fair value	61,082	70,478
Basis of Fair Value Measurement, Level 1 | Deferred Compensation Assets | Other Assets
Assets:
Assets, fair value	36,307	35,510
Basis of Fair Value Measurement, Level 1 | Deferred Compensation Liability | Other Noncurrent Liabilities
Liabilities:
Liabilities, fair value	36,307	35,510
Basis of Fair Value Measurement, Level 2
Assets:
Assets, fair value	543,181	10,343
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	$ 3,181	$ 10,343