v3.26.3
Segment Reporting Information by Segment (Detail) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Dec. 31, 2025
Segment Reporting Information [Line Items]          
Revenues $ 7,936.5 $ 6,671.8 $ 22,259.7 $ 21,624.0  
Cost of sales and revenues 6,311.0 5,345.4 17,716.5 17,231.8  
Research and development 108.9 111.0 332.3 339.3  
Selling, general and administrative 167.8 180.2 536.8 541.1  
Interest and other borrowing expenses 181.5 201.0 544.2 591.9  
Depreciation and other expenses 168.2 161.7 493.5 476.3  
Provision for losses on receivables 28.6 36.5 112.1 84.0  
Other segment (income) expenses, net (26.5) (16.8) (64.1) 299.5  
Income (Loss) before investment income and income taxes 997.0 652.8 2,588.4 2,060.1  
Investment income 84.0 90.8 250.4 258.5  
Total Income (Loss) Before Income Taxes 1,081.0 743.6 2,838.8 2,318.6  
Depreciation and amortization 216.5 205.8 631.6 618.2  
Expenditures for long-lived assets 424.4 295.7 1,115.7 1,016.2  
Assets 45,138.4   45,138.4   $ 44,336.2
Operating Segments          
Segment Reporting Information [Line Items]          
Revenues 8,056.2 6,763.6 22,698.8 22,015.6  
Intersegment          
Segment Reporting Information [Line Items]          
Revenues (119.7) (91.8) (439.1) (391.6)  
Truck, Parts and Other          
Segment Reporting Information [Line Items]          
Net sales and revenues 7,377.6 6,106.5 20,608.9 19,983.0  
Revenues 7,377.6 6,106.5 20,608.9 19,983.0  
Cost of sales and revenues 6,311.0 5,345.4 17,716.5 17,231.8  
Research and development 108.9 111.0 332.3 339.3  
Selling, general and administrative 125.3 140.3 413.5 422.8  
Other segment (income) expenses, net (26.5) (16.8) (64.1) 299.5  
Income (Loss) before investment income and income taxes 858.9 526.6 2,210.7 1,689.6  
Total Income (Loss) Before Income Taxes 858.9 526.6 2,210.7 1,689.6  
Depreciation and amortization 117.8 99.9 334.8 303.6  
Expenditures for long-lived assets 135.5 152.7 420.5 554.6  
Assets 22,662.5   22,662.5   21,532.8
Cash and marketable securities 9,238.2   9,238.2   9,253.7
Truck, Parts and Other | Operating Segments          
Segment Reporting Information [Line Items]          
Net sales and revenues 7,497.3 6,198.3 21,048.0 20,374.6  
Truck, Parts and Other | Intersegment          
Segment Reporting Information [Line Items]          
Net sales and revenues (119.7) (91.8) (439.1) (391.6)  
Truck, Parts and Other | Truck          
Segment Reporting Information [Line Items]          
Net sales and revenues 5,602.4 4,381.4 15,382.0 14,850.3  
Cost of sales and revenues 5,032.3 4,125.8 13,999.9 13,630.1  
Research and development 73.7 79.6 226.2 246.9  
Selling, general and administrative 43.4 63.3 154.8 175.3  
Other segment (income) expenses, net (1.5) 10.2 9.9 21.8  
Income (Loss) before investment income and income taxes 454.5 102.5 991.2 776.2  
Total Income (Loss) Before Income Taxes 454.5 102.5 991.2 776.2  
Depreciation and amortization 106.7 89.6 300.8 273.6  
Expenditures for long-lived assets 119.8 137.1 359.6 512.6  
Assets 8,772.9   8,772.9   7,966.1
Truck, Parts and Other | Truck | Operating Segments          
Segment Reporting Information [Line Items]          
Net sales and revenues 5,706.3 4,455.9 15,766.7 15,187.6  
Truck, Parts and Other | Truck | Intersegment          
Segment Reporting Information [Line Items]          
Net sales and revenues (103.9) (74.5) (384.7) (337.3)  
Truck, Parts and Other | Parts          
Segment Reporting Information [Line Items]          
Net sales and revenues 1,780.0 1,724.6 5,237.0 5,135.4  
Cost of sales and revenues 1,272.3 1,216.5 3,702.3 3,592.7  
Research and development 35.2 31.4 106.1 92.4  
Selling, general and administrative 66.9 66.5 202.4 192.0  
Other segment (income) expenses, net 1.2 0.2 2.5 5.3  
Income (Loss) before investment income and income taxes 404.4 410.0 1,223.7 1,253.0  
Total Income (Loss) Before Income Taxes 404.4 410.0 1,223.7 1,253.0  
Depreciation and amortization 4.7 4.3 15.1 11.5  
Expenditures for long-lived assets 3.2 8.3 12.7 14.7  
Assets 2,438.8   2,438.8   2,278.5
Truck, Parts and Other | Parts | Operating Segments          
Segment Reporting Information [Line Items]          
Net sales and revenues 1,795.8 1,741.9 5,291.4 5,189.7  
Truck, Parts and Other | Parts | Intersegment          
Segment Reporting Information [Line Items]          
Net sales and revenues (15.8) (17.3) (54.4) (54.3)  
Truck, Parts and Other | Other          
Segment Reporting Information [Line Items]          
Net sales and revenues (4.8) 0.5 (10.1) (2.7)  
Cost of sales and revenues 6.4 3.1 14.3 9.0  
Selling, general and administrative 15.0 10.5 56.3 55.5  
Other segment (income) expenses, net (26.2) (27.2) (76.5) 272.4  
Income (Loss) before investment income and income taxes   14.1 (4.2) (339.6)  
Total Income (Loss) Before Income Taxes   14.1 (4.2) (339.6)  
Depreciation and amortization 6.4 6.0 18.9 18.5  
Expenditures for long-lived assets 12.5 7.3 48.2 27.3  
Assets 2,212.6   2,212.6   2,034.5
Truck, Parts and Other | Other | Operating Segments          
Segment Reporting Information [Line Items]          
Net sales and revenues (4.8) 0.5 (10.1) (2.7)  
Financial Services          
Segment Reporting Information [Line Items]          
Revenues 558.9 565.3 1,650.8 1,641.0  
Selling, general and administrative 42.5 39.9 123.3 118.3  
Interest and other borrowing expenses 181.5 201.0 544.2 591.9  
Depreciation and other expenses 168.2 161.7 493.5 476.3  
Provision for losses on receivables 28.6 36.5 112.1 84.0  
Income (Loss) before investment income and income taxes 138.1 126.2 377.7 370.5  
Total Income (Loss) Before Income Taxes 138.1 126.2 377.7 370.5  
Depreciation and amortization 98.7 105.9 296.8 314.6  
Expenditures for long-lived assets 288.9 143.0 695.2 461.6  
Assets 22,475.9   22,475.9   $ 22,803.4
Financial Services | Operating Segments          
Segment Reporting Information [Line Items]          
Revenues $ 558.9 $ 565.3 $ 1,650.8 $ 1,641.0