XML 126 R30.htm IDEA: XBRL DOCUMENT v3.22.1
Fair Value Measurements - Reconciliation of Our Investment in Restricted Equity Securities Measured at Fair Value on Quarterly Basis Using Significant Unobservable Inputs (Level 3) (Detail) - Equity Securities - Level 3 - Fair Value, Recurring - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2022
Mar. 31, 2021
Fair Value, Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Roll Forward]    
Balance at beginning of period $ 11.0 $ 38.2
Unrealized gain included in earnings 20.8 0.7
Transfers out of Level 3 (31.8) 0.0
Balance at end of period $ 0.0 $ 38.9