Significant Accounting Policies Activity in Polaris Accrued Warranty Reserve (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Activity in Product Warranty Reserve [Roll Forward]
Balance at beginning of period	$ 142.2	$ 134.2	$ 140.8	$ 136.2
Additions charged to expense	26.9	37.2	97.3	91.2
Warranty claims paid, net	(32.0)	(30.8)	(101.0)	(86.8)
Balance at end of period	$ 137.1	$ 140.6	$ 137.1	$ 140.6