Quarterly Results (Unaudited) (Detail) $ / shares in Units, € in Millions, $ in Millions		3 Months Ended								6 Months Ended		12 Months Ended
		Dec. 31, 2016 USD ($) $ / shares	Sep. 30, 2016 USD ($) $ / shares	Jun. 30, 2016 USD ($) $ / shares	Mar. 31, 2016 USD ($) $ / shares	Dec. 31, 2015 USD ($) $ / shares	Sep. 30, 2015 USD ($) $ / shares	Jun. 30, 2015 USD ($) $ / shares	Mar. 31, 2015 USD ($) $ / shares	Jun. 30, 2016 USD ($)	Jun. 30, 2016 EUR (€)	Dec. 31, 2016 USD ($) $ / shares	Dec. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($) $ / shares
Quarterly Financial Information [Line Items]
Net (Loss) Income		$ 288.8	$ 346.2	$ 481.3	$ (594.6)	$ 347.2	$ 431.2	$ 447.2	$ 378.4			$ 521.7	$ 1,604.0	$ 1,358.8
Adjusted Net Income	[1]			$ 371.7	$ 348.0
Net (Loss) Income Per Share:
Basic | $ / shares		$ 0.82	$ 0.99	$ 1.37	$ (1.69)	$ 0.98	$ 1.21	$ 1.26	$ 1.07			$ 1.49	$ 4.52	$ 3.83
Diluted | $ / shares		$ 0.82	$ 0.98	1.37	(1.69)	$ 0.98	$ 1.21	$ 1.26	$ 1.06			$ 1.48	$ 4.51	$ 3.82
Adjusted Diluted | $ / shares	[1]			$ 1.06	$ 0.99
Truck, Parts and Other
Quarterly Financial Information [Line Items]
Net sales and revenues		$ 3,767.0	$ 3,953.2	$ 4,115.8	$ 4,010.6	$ 4,062.5	$ 4,546.2	$ 4,786.1	$ 4,548.0			$ 15,846.6	$ 17,942.8	$ 17,792.8
Cost of sales and revenues		3,243.2	3,371.5	3,489.4	3,413.6	3,469.4	3,851.3	4,061.2	3,910.2			13,517.7	15,292.1	15,481.6
Research and development		67.6	59.2	60.8	59.6	66.7	57.6	59.3	56.2			247.2	239.8	215.6
European Commission charge				(109.6)	942.6					$ 833.0	€ 752.7	833.0	0.0	0.0
Financial Services
Quarterly Financial Information [Line Items]
Revenues		303.7	296.2	297.4	289.4	292.8	301.0	293.8	284.7			1,186.7	1,172.3	1,204.2
Interest and other borrowing expenses		32.1	32.2	32.6	30.3	30.1	29.2	29.6	29.1			127.2	118.0	133.7
Depreciation and other expenses		$ 165.3	$ 162.6	$ 156.4	$ 150.9	$ 144.9	$ 152.5	$ 145.9	$ 140.4			$ 635.2	$ 583.7	$ 588.5

[1] See Reconciliation of GAAP to Non-GAAP Financial Measures for 2016 on page 33.