Quarterly Financial Data Items affecting quarter results (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015
After-tax restructuring and related costs	$ 1.4	$ 0.2	$ 4.0	$ 0.8
After-tax business development and related costs	16.2	3.1	1.8	0.3	$ 0.8	$ 1.3	$ 0.5	$ 9.5
After-tax gain on sale of assets		0.4	0.2	0.1	0.2	0.9	$ 0.3	0.2
After-tax write off of debt issuance costs	0.5							1.3
After-tax loss on settlement of foreign currency forward purchase contracts								11.6
After tax loss on sale and impairment of assets	0.8
Adjustment for income tax returns from previous fiscal year						$ 0.4
After-tax out of period impact of final allocation of fair values to assets and liabilities					1.6
Income tax expense due to the application of the full year effective tax rate					(1.3)
Australian Operations [Member]
After tax asset impairment and related charges				16.8
After-tax restructuring and related costs								$ 1.2
U.K./European Operations [Member]
After-tax acquisition/integration related costs					0.9
Internal Revenue Service (IRS) [Member]
Tax benefit associated with the United States Short Line Tax Credit	7.5	7.8	$ 7.2	$ 6.3	27.4
Her Majesty's Revenue and Customs (HMRC) [Member]
Tax benefit from tax rate adjustment		$ 4.3			$ 9.7
ERS Railways [Member]
After tax asset impairment and related charges	21.5
UNITED KINGDOM
After-tax restructuring and related costs	$ 8.6