Segment, Geographic and Product Family Information Information Regarding Operations by Geographic Area and Product Family (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2017	Oct. 31, 2016
Segment Reporting Information [Line Items]
Net revenue	$ 515.3	$ 489.6	$ 1,502.8	$ 1,552.2
Architecture, Engineering and Construction
Segment Reporting Information [Line Items]
Net revenue	215.4	212.3	628.7	684.4
Manufacturing
Segment Reporting Information [Line Items]
Net revenue	146.9	146.6	436.0	481.5
AutoCAD and AutoCAD LT
Segment Reporting Information [Line Items]
Net revenue	102.7	80.1	290.7	239.1
Media and Entertainment
Segment Reporting Information [Line Items]
Net revenue	37.7	34.2	112.1	103.6
Other
Segment Reporting Information [Line Items]
Net revenue	12.6	16.4	35.3	43.6
U.S.
Segment Reporting Information [Line Items]
Net revenue	182.4	182.2	546.8	562.1
Other Americas
Segment Reporting Information [Line Items]
Net revenue	32.2	31.1	91.9	99.0
Americas
Segment Reporting Information [Line Items]
Net revenue	214.6	213.3	638.7	661.1
Europe, Middle East and Africa
Segment Reporting Information [Line Items]
Net revenue	205.4	191.0	594.4	614.1
Asia Pacific
Segment Reporting Information [Line Items]
Net revenue	$ 95.3	$ 85.3	$ 269.7	$ 277.0