Victory Motorcycles Wind Down - Narrative (Detail) - Victory Motorcycles - Disposal Group, Disposed of by Means Other than Sale, Not Discontinued Operations, Abandonment - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Charges related to the wind down plan	$ 59,792,000
Promotional charges	21,184,000
Gain from sale of cost method investments	(3,570,000)
Total impact of wind down activities	77,406,000
Liability balance	5,645,000	$ 0
Minimum
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Estimated charges	10,000,000
Maximum
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Estimated charges	$ 10,000,000