Significant Accounting Policies Activity in Polaris Accrued Warranty Reserve (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Accounting Policies [Abstract]
Deferred tax liabilities	$ 4,741		$ 4,741		$ 6,490
Activity in Product Warranty Reserve [Roll Forward]
Balance at beginning of period	132,758	$ 106,155	121,824	$ 123,840
Additions to reserve related to acquisitions	0	13,799	8,809	13,799
Additions charged to expense	31,359	37,741	94,232	79,913
Warranty claims paid, net	(27,003)	(35,151)	(87,751)	(95,008)
Balance at end of period	$ 137,114	$ 122,544	$ 137,114	$ 122,544