Basis of Presentation Reclassification (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended	9 Months Ended
	Oct. 31, 2015	Jul. 31, 2015	Oct. 31, 2014	Jul. 31, 2015	Oct. 31, 2015	Oct. 31, 2014
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Income tax expense	$ 21.3	$ 269.5	$ 0.9	$ 272.2	$ 293.5	$ 19.8
Operating Expenses	$ 523.6		$ 517.4		1,569.0	$ 1,488.3
Employee Benefits and Estimated Personal Property Liabilities
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Operating Expenses					$ 5.7
Restatement Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Income tax expense		$ 33.1		$ 33.1