Revenue (Contract Liabilities) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jul. 01, 2018	Jul. 01, 2018	Jan. 01, 2018
Contract with Customer, Liability [Abstract]
Contract with Customer, Liability			$ 23.4
Contract with Customer, Liability, Revenue Recognized	$ 5.1	$ 9.1
Licensing | Motorcycles and Related Products
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period		6 years
Financial Services Other income | Financial Services
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period		6 years
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period		1 year
Revenue, Remaining Performance Obligation	10.8	$ 10.8
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period		1 year
Revenue, Remaining Performance Obligation	9.8	$ 9.8
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period
Revenue, Remaining Performance Obligation	$ 30.8	$ 30.8