Summary of Significant Accounting Policies (New Accounting Standards) (Impact of Adoption of ASU 2014-09) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018
New Accounting Pronouncements or Change in Accounting Principle
Revenues	$ 5,716,875	$ 5,647,224	$ 5,996,458
Motorcycles and Related Products cost of goods sold	3,351,796	3,272,330	3,425,997
Operating income	713,523	882,081	1,046,294
Income before provision for income taxes	686,629	863,839	1,023,911
Provision for income taxes	155,178	342,080	331,747
Net income	531,451	521,759	692,164
Other current assets	144,368	175,853
Deferred income taxes	141,464	109,073
Accrued liabilities	601,130	529,822
Retained earnings	2,007,583	1,607,570
Calculated under Revenue Guidance in Effect before Topic 606 | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle
Motorcycles and Related Products cost of goods sold	3,348,779
Operating income	717,842
Income before provision for income taxes	690,948
Provision for income taxes	156,225
Net income	534,723
Other current assets	163,841
Deferred income taxes	143,312
Accrued liabilities	625,203
Retained earnings	2,004,831
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle
Motorcycles and Related Products cost of goods sold	3,017
Operating income	(4,319)
Income before provision for income taxes	(4,319)
Provision for income taxes	(1,047)
Net income	(3,272)
Other current assets	(19,473)
Deferred income taxes	(1,848)
Accrued liabilities	(24,073)
Retained earnings	2,752			$ 6,000
Motorcycles and Related Products
New Accounting Pronouncements or Change in Accounting Principle
Revenues	4,968,646	$ 4,915,027	$ 5,271,376
Motorcycles and Related Products | Calculated under Revenue Guidance in Effect before Topic 606 | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle
Revenues	4,969,948
Motorcycles and Related Products | Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle
Revenues	$ (1,302)