Fair value measurements - Narrative (Detail) |
1 Months Ended | 3 Months Ended | 9 Months Ended | ||||
---|---|---|---|---|---|---|---|
Jan. 31, 2021
USD ($)
|
Sep. 30, 2021
USD ($)
|
Sep. 30, 2020
USD ($)
|
Sep. 30, 2021
USD ($)
|
Sep. 30, 2020
USD ($)
|
Nov. 04, 2021
company
|
Dec. 31, 2020
USD ($)
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |||||||
Realized gain (loss) on available-for-sale securities | $ 0 | $ 0 | $ 0 | $ 0 | |||
Interest receivable | 1,200,000 | 1,200,000 | $ 3,100,000 | ||||
Interest receivable, write-offs | 0 | 0 | 0 | 0 | |||
Investment at fair value | 3,100,000 | 3,100,000 | $ 5,653,000 | ||||
Proceeds from sale of equity securities | $ 31,300,000 | ||||||
Subsequent Event | |||||||
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |||||||
Number of independent publicly traded companies | company | 2 | ||||||
Other (Expense) Income, Net | |||||||
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |||||||
Unrealized gain (loss) on equity securities | $ (500,000) | $ 5,800,000 | $ (28,800,000) | $ 9,100,000 |