Acquisitions (Unaudited Pro Forma Results of Acquirees) (Details) - PlanGrid - USD ($) $ in Millions	12 Months Ended
	Jan. 31, 2019	Jan. 31, 2018
Business Acquisition [Line Items]
Total revenues	$ 2,632.6	$ 2,099.2
Pretax loss	(157.5)	(724.9)
Net loss	$ (200.1)	$ (734.5)