Write-downs, Reserves, and Project Opening Costs, net of Recoveries (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Write-downs and reserves, net of recoveries:
Remediation costs	$ 28.5	$ 21.1	$ 11.0
Divestitures and abandonments	22.8	59.1	10.1
Efficiency projects	0	17.5	46.6
Gain on ThistleDown transactions (Note 4)	0	(11.0)	0
Suffolk Downs equity investment write-off (Note 4)	41.9	0	0
Project opening costs	15.4	12.6	4.7
Other	(4.2)	0.4	1.4
Total	$ 104.4	$ 99.7	$ 73.8