Segment Reporting Information by Segment (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Revenues		$ 35,127.4	$ 28,819.7	$ 23,522.3
Investment income		292.2	61.0	15.5
Total Income Before Income Taxes		5,718.2	3,848.7	2,396.3
Depreciation and amortization		923.9	790.2	903.3
Expenditures for long-lived assets		1,265.9	1,370.5	1,585.5
Assets		40,823.4	33,275.5	29,509.4
Truck, Parts and Other
Segment Reporting Information [Line Items]
Net sales and revenues		33,315.5	27,314.3	21,834.5
Revenues		33,315.5	27,314.3	21,834.5
Income (loss) before income taxes		4,885.7	3,198.8	1,943.2
Depreciation and amortization		443.8	362.8	311.5
Expenditures for long-lived assets		683.7	515.7	600.7
Assets		19,859.5	16,095.9	14,090.5
Cash and marketable securities		8,659.3	6,158.9	4,813.0
Truck, Parts and Other | Trucks
Segment Reporting Information [Line Items]
Net sales and revenues		26,846.4	21,486.2	16,799.7
Income (loss) before income taxes		3,799.9	1,753.3	804.9
Depreciation and amortization		403.5	324.9	277.6
Expenditures for long-lived assets		584.8	466.0	547.2
Assets		8,038.5	7,218.1	6,912.1
Truck, Parts and Other | Trucks | Operating Segments
Segment Reporting Information [Line Items]
Net sales and revenues		27,257.1	22,005.5	17,379.0
Truck, Parts and Other | Trucks | Intersegment
Segment Reporting Information [Line Items]
Net sales and revenues		(410.7)	(519.3)	(579.3)
Truck, Parts and Other | Parts Subsegment
Segment Reporting Information [Line Items]
Net sales and revenues		6,414.4	5,764.3	4,944.3
Income (loss) before income taxes		1,702.6	1,446.6	1,110.0
Depreciation and amortization		15.0	14.0	12.0
Expenditures for long-lived assets		65.7	21.1	29.4
Assets		1,912.1	1,742.1	1,505.1
Truck, Parts and Other | Parts Subsegment | Operating Segments
Segment Reporting Information [Line Items]
Net sales and revenues		6,486.5	5,829.4	5,004.8
Truck, Parts and Other | Parts Subsegment | Intersegment
Segment Reporting Information [Line Items]
Net sales and revenues		(72.1)	(65.1)	(60.5)
Truck, Parts and Other | Other
Segment Reporting Information [Line Items]
Net sales and revenues		54.7	63.8	90.5
Income (loss) before income taxes	[1]	(616.8)	(1.1)	28.3
Depreciation and amortization		25.3	23.9	21.9
Expenditures for long-lived assets		33.2	28.6	24.1
Cash and marketable securities		1,249.6	976.8	860.3
Financial Services
Segment Reporting Information [Line Items]
Revenues		1,811.9	1,505.4	1,687.8
Income (loss) before income taxes		540.3	588.9	437.6
Depreciation and amortization		480.1	427.4	591.8
Expenditures for long-lived assets		582.2	854.8	984.8
Assets		$ 20,963.9	$ 17,179.6	$ 15,418.9

[1] In 2023, Other includes a $600.0 million non-recurring charge related to civil litigation in Europe (EC-related claims) which is discussed in Note L