The Company and Significant Accounting Policies - Fair Value Assets and Liabilities Measured on Recurring Basis (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Contingent Consideration
Liabilities:
Fair Value and Carrying Value on Liabilities	$ 104.7
Money Market Account
Assets:
Fair Value and Carrying Value on Assets	88.3	$ 59.9
Certificates of Deposit
Assets:
Fair Value and Carrying Value on Assets		2.8
Corporate Bonds
Assets:
Fair Value and Carrying Value on Assets		25.2
Level 2 | Money Market Account
Assets:
Fair Value and Carrying Value on Assets	88.3	59.9
Level 2 | Certificates of Deposit
Assets:
Fair Value and Carrying Value on Assets		2.8
Level 2 | Corporate Bonds
Assets:
Fair Value and Carrying Value on Assets		$ 25.2
Level 3 | Contingent Consideration
Liabilities:
Fair Value and Carrying Value on Liabilities	$ 104.7