Significant Accounting Policies Activity in Polaris Accrued Warranty Reserve (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Accounting Policies [Abstract]
Deferred tax liabilities	$ 5,847		$ 6,490
Activity in Product Warranty Reserve [Roll Forward]
Balance at beginning of period	121,824	$ 123,840
Additions charged to expense	26,019	16,031
Warranty claims paid, net	(31,626)	(23,585)
Balance at end of period	$ 116,217	$ 116,286