Investments - Narrative (Detail) |
12 Months Ended | ||
|---|---|---|---|
|
Dec. 31, 2019
USD ($)
security
|
Dec. 31, 2018
USD ($)
|
Dec. 31, 2017
USD ($)
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |||
| Contractual maturities term (maximum) | 36 months | ||
| Number of available-for-sale securities in unrealized loss position | security | 91 | ||
| Other-than-temporary impairments considered | $ 0 | ||
| Unrealized gain recognized on sale of marketable equity securities | $ 10,700,000 | ||
| Tax effect recognized on sale of marketable equity securities | $ 3,500,000 | ||
| Debt and equity investments in privately-held companies included in other assets | 22,400,000 | $ 14,600,000 | |
| Marketable equity securities | |||
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |||
| Proceeds from sale of marketable equity securities | 40,000,000.0 | ||
| Realized gain recognized on sale of marketable equity securities | 19,300,000 | ||
| Marketable securities | $ 0 | $ 0 | |