Segment Reporting - Selected Financial Data for Each of Operating Segments (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Segment Reporting Information [Line Items]
Revenue	$ 2,362.1	$ 662.5	$ 4,281.0	$ 1,525.9
Operating income (loss)	44.1	(13.6)	9.4	(46.9)
Depreciation and amortization	102.1	27.2	191.9	63.8
Interest expense	61.5	17.8	120.9	31.3
Tax expense (benefit)	1.9	(20.1)	(21.3)	(25.2)
Goodwill	3,445.0	918.5	3,445.0	918.5	$ 929.3
Operating Segments | Transportation
Segment Reporting Information [Line Items]
Revenue	1,396.8	612.4	2,820.4	1,475.8
Operating income (loss)	30.9	4.9	57.7	8.2
Depreciation and amortization	54.8	23.2	103.6	58.6
Interest expense	0.0	0.3	0.0	0.3
Tax expense (benefit)	0.0	0.0	0.0	0.7
Goodwill	1,857.8	566.3	1,857.8	566.3	577.0
Operating Segments | Logistics
Segment Reporting Information [Line Items]
Revenue	993.3	50.1	1,493.7	50.1
Operating income (loss)	36.0	4.5	46.9	4.5
Depreciation and amortization	46.9	3.5	87.2	3.4
Interest expense	0.0	0.0	0.0	0.0
Tax expense (benefit)	0.0	0.0	0.0	0.0
Goodwill	1,587.2	352.2	1,587.2	352.2	$ 352.3
Corporate
Segment Reporting Information [Line Items]
Revenue	0.0	0.0	0.0	0.0
Operating income (loss)	(22.8)	(23.0)	(95.2)	(59.6)
Depreciation and amortization	0.4	0.5	1.1	1.8
Interest expense	61.5	17.5	120.9	31.0
Tax expense (benefit)	1.9	(20.1)	(21.3)	(25.9)
Goodwill	0.0	0.0	0.0	0.0
Eliminations
Segment Reporting Information [Line Items]
Revenue	(28.0)	0.0	(33.1)	0.0
Operating income (loss)	0.0	0.0	0.0	0.0
Depreciation and amortization	0.0	0.0	0.0	0.0
Interest expense	0.0	0.0	0.0	0.0
Tax expense (benefit)	0.0	0.0	0.0	0.0
Goodwill	$ 0.0	$ 0.0	$ 0.0	$ 0.0