Accumulated Other Comprehensive Loss (Reclassifications from Accumulated Other Comprehensive Loss) (Details) $ in Millions	3 Months Ended
	Apr. 30, 2016 USD ($)
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net periodic benefit cost	$ 3
Income tax benefit	(1)
Net of tax	2
Pension Benefits [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net periodic benefit cost	4
Postretirement Benefits [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net periodic benefit cost	$ (1)