Restructuring Expense (Narrative) (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended		1 Months Ended	6 Months Ended		1 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2013 2011 Restructuring Plan [Member] New Castalloy Faciltiy [Member] employee	Feb. 28, 2011 2011 Restructuring Plan [Member] Kansas City Facility [Member]	Jun. 30, 2013 2011 Restructuring Plan [Member] Kansas City Facility [Member]	Jun. 30, 2013 Original 2011 Restructuring Plan [Member] New Castalloy Faciltiy [Member]	Sep. 30, 2010 2010 Restructuring Plan [Member] agreement	Jun. 30, 2013 2010 Restructuring Plan [Member]	Jun. 30, 2013 2010 Restructuring Plan [Member] Milwaukee Facilities [Member]	Jun. 30, 2013 2010 Restructuring Plan [Member] Tomahawk Facilities [Member]	Jun. 30, 2013 2009 Restructuring Plan [Member]	Jun. 30, 2013 2009 Restructuring Plan [Member] Production [Member] Hourly [Member] Minimum [Member]	Jun. 30, 2013 2009 Restructuring Plan [Member] Production [Member] Hourly [Member] Maximum [Member]	Jun. 30, 2013 2009 Restructuring Plan [Member] Motorcycles [Member] Non-Production [Member] Salaried [Member]	Jun. 30, 2013 2009 Restructuring Plan [Member] Financial Services [Member] Non-Production [Member] Salaried [Member]
Restructuring Cost and Reserve [Line Items]
Document Fiscal Year Focus	2013
Estimated reduction in workforce		100		145	200			250	75		2,700	2,900	800	100
Restructuring and Related Cost, Expected Number Of Workforce Positions Retained		100
Estimated restructuring expense		$ 21.3								$ 397.9
Non-cash charges		35.00%								30.00%
Cost incurred to date		$ 20.5		$ 6.5			$ 59.3			$ 395.5
Labor agreement period (in years)			7 years			7 years
Cost incurred to date, non-cash				10.00%			45.00%
Number of labor agreements						3