v3.26.1
Segment Reporting Information by Segment (Detail) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Dec. 31, 2025
Segment Reporting Information [Line Items]          
Revenues $ 7,546.7 $ 7,510.5 $ 14,323.2 $ 14,952.2  
Cost of sales and revenues 5,989.0 5,995.4 11,405.5 11,886.4  
Research and development 114.3 112.9 223.4 228.3  
Selling, general and administrative 179.7 179.3 369.0 360.9  
Interest and other borrowing expenses 179.9 200.3 362.7 390.9  
Depreciation and other expenses 165.2 154.9 325.3 314.6  
Provision for losses on receivables 39.4 29.2 83.5 47.5  
Other segment expenses (income), net (16.3) (9.5) (37.6) 316.3  
Income (Loss) before investment income and income taxes 895.5 848.0 1,591.4 1,407.3  
Investment income 86.0 83.9 166.4 167.7  
Total Income (Loss) Before Income Taxes 981.5 931.9 1,757.8 1,575.0  
Depreciation and amortization 215.0 207.3 415.1 412.4  
Expenditures for long-lived assets 385.1 387.9 691.3 720.5  
Assets 43,980.1   43,980.1   $ 44,336.2
Operating Segments          
Segment Reporting Information [Line Items]          
Revenues 7,700.3 7,626.5 14,642.6 15,252.0  
Intersegment          
Segment Reporting Information [Line Items]          
Revenues (153.6) (116.0) (319.4) (299.8)  
Truck, Parts and Other          
Segment Reporting Information [Line Items]          
Net sales and revenues 6,997.0 6,962.8 13,231.3 13,876.5  
Revenues 6,997.0 6,962.8 13,231.3 13,876.5  
Cost of sales and revenues 5,989.0 5,995.4 11,405.5 11,886.4  
Research and development 114.3 112.9 223.4 228.3  
Selling, general and administrative 138.6 139.2 288.2 282.5  
Other segment expenses (income), net (16.3) (9.5) (37.6) 316.3  
Income (Loss) before investment income and income taxes 771.4 724.8 1,351.8 1,163.0  
Total Income (Loss) Before Income Taxes 771.4 724.8 1,351.8 1,163.0  
Depreciation and amortization 114.0 102.4 217.0 203.7  
Expenditures for long-lived assets 142.5 221.8 285.0 401.9  
Assets 21,714.6   21,714.6   21,532.8
Cash and marketable securities 8,667.4   8,667.4   9,253.7
Truck, Parts and Other | Operating Segments          
Segment Reporting Information [Line Items]          
Net sales and revenues 7,150.6 7,078.8 13,550.7 14,176.3  
Truck, Parts and Other | Intersegment          
Segment Reporting Information [Line Items]          
Net sales and revenues (153.6) (116.0) (319.4) (299.8)  
Truck, Parts and Other | Truck          
Segment Reporting Information [Line Items]          
Net sales and revenues 5,253.1 5,243.1 9,779.6 10,468.9  
Cost of sales and revenues 4,758.8 4,787.8 8,967.6 9,504.3  
Research and development 78.9 81.9 152.5 167.3  
Selling, general and administrative 50.0 54.7 111.4 112.0  
Other segment expenses (income), net 4.9 9.9 11.4 11.6  
Income (Loss) before investment income and income taxes 360.5 308.8 536.7 673.7  
Total Income (Loss) Before Income Taxes 360.5 308.8 536.7 673.7  
Depreciation and amortization 101.7 93.1 194.1 184.0  
Expenditures for long-lived assets 114.6 213.4 239.8 375.5  
Assets 8,461.1   8,461.1   7,966.1
Truck, Parts and Other | Truck | Operating Segments          
Segment Reporting Information [Line Items]          
Net sales and revenues 5,388.1 5,340.9 10,060.4 10,731.7  
Truck, Parts and Other | Truck | Intersegment          
Segment Reporting Information [Line Items]          
Net sales and revenues (135.0) (97.8) (280.8) (262.8)  
Truck, Parts and Other | Parts          
Segment Reporting Information [Line Items]          
Net sales and revenues 1,746.9 1,720.9 3,457.0 3,410.8  
Cost of sales and revenues 1,226.3 1,204.7 2,430.0 2,376.2  
Research and development 35.4 31.0 70.9 61.0  
Selling, general and administrative 67.8 64.6 135.5 125.5  
Other segment expenses (income), net 0.4 4.1 1.3 5.1  
Income (Loss) before investment income and income taxes 417.0 416.5 819.3 843.0  
Total Income (Loss) Before Income Taxes 417.0 416.5 819.3 843.0  
Depreciation and amortization 5.9 2.9 10.4 7.2  
Expenditures for long-lived assets 4.4 3.1 9.5 6.4  
Assets 2,366.0   2,366.0   2,278.5
Truck, Parts and Other | Parts | Operating Segments          
Segment Reporting Information [Line Items]          
Net sales and revenues 1,765.5 1,739.1 3,495.6 3,447.8  
Truck, Parts and Other | Parts | Intersegment          
Segment Reporting Information [Line Items]          
Net sales and revenues (18.6) (18.2) (38.6) (37.0)  
Truck, Parts and Other | Other          
Segment Reporting Information [Line Items]          
Net sales and revenues (3.0) (1.2) (5.3) (3.2)  
Cost of sales and revenues 3.9 2.9 7.9 5.9  
Selling, general and administrative 20.8 19.9 41.3 45.0  
Other segment expenses (income), net (21.6) (23.5) (50.3) 299.6  
Income (Loss) before investment income and income taxes (6.1) (0.5) (4.2) (353.7)  
Total Income (Loss) Before Income Taxes (6.1) (0.5) (4.2) (353.7)  
Depreciation and amortization 6.4 6.4 12.5 12.5  
Expenditures for long-lived assets 23.5 5.3 35.7 20.0  
Assets 2,220.1   2,220.1   2,034.5
Truck, Parts and Other | Other | Operating Segments          
Segment Reporting Information [Line Items]          
Net sales and revenues (3.0) (1.2) (5.3) (3.2)  
Financial Services          
Segment Reporting Information [Line Items]          
Revenues 549.7 547.7 1,091.9 1,075.7  
Selling, general and administrative 41.1 40.1 80.8 78.4  
Interest and other borrowing expenses 179.9 200.3 362.7 390.9  
Depreciation and other expenses 165.2 154.9 325.3 314.6  
Provision for losses on receivables 39.4 29.2 83.5 47.5  
Income (Loss) before investment income and income taxes 124.1 123.2 239.6 244.3  
Total Income (Loss) Before Income Taxes 124.1 123.2 239.6 244.3  
Depreciation and amortization 101.0 104.9 198.1 208.7  
Expenditures for long-lived assets 242.6 166.1 406.3 318.6  
Assets 22,265.5   22,265.5   $ 22,803.4
Financial Services | Operating Segments          
Segment Reporting Information [Line Items]          
Revenues $ 549.7 $ 547.7 $ 1,091.9 $ 1,075.7