Segment Information - Segment Financial Information (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Total sales	$ 2,001.7	$ 1,077.8	$ 5,831.6	$ 3,245.7
Income (loss) from operations	169.1	125.2	437.0	380.0
Interest expense and other, net	(55.8)	(22.5)	(164.9)	(69.9)
Income from operations before income taxes	113.3	102.7	272.1	310.1
Freight Segment
Segment Reporting Information [Line Items]
Total sales	1,295.7	391.6	3,666.1	1,183.4
Transit Segment
Segment Reporting Information [Line Items]
Total sales	706.0	686.2	2,165.5	2,062.3
Corporate Activities and Elimination
Segment Reporting Information [Line Items]
Total sales	(25.2)	(18.3)	(69.1)	(55.8)
Income (loss) from operations	(34.8)	(15.0)	(124.2)	(40.2)
Interest expense and other, net	(55.8)	(22.5)	(164.9)	(69.9)
Income from operations before income taxes	(90.6)	(37.5)	(289.1)	(110.1)
Corporate Activities and Elimination \| Freight Segment
Segment Reporting Information [Line Items]
Total sales	14.1	13.5	44.5	44.2
Corporate Activities and Elimination \| Transit Segment
Segment Reporting Information [Line Items]
Total sales	11.1	4.8	24.6	11.6
Operating Segments \| Freight Segment
Segment Reporting Information [Line Items]
Total sales	1,309.8	405.1	3,710.6	1,227.6
Income (loss) from operations	148.1	79.4	375.3	233.4
Interest expense and other, net	0.0	0.0	0.0	0.0
Income from operations before income taxes	148.1	79.4	375.3	233.4
Operating Segments \| Transit Segment
Segment Reporting Information [Line Items]
Total sales	717.1	691.0	2,190.1	2,073.9
Income (loss) from operations	55.8	60.7	185.9	186.8
Interest expense and other, net	0.0	0.0	0.0	0.0
Income from operations before income taxes	$ 55.8	$ 60.7	$ 185.9	$ 186.8

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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