Segment, Geographic and Product Family Information Information Regarding Operations by Geographic Area and Product Family (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2017	Jul. 31, 2016
Segment Reporting Information [Line Items]
Net revenue	$ 501.8	$ 550.7	$ 987.5	$ 1,062.6
Architecture, Engineering and Construction
Segment Reporting Information [Line Items]
Net revenue	208.8	253.2	413.3	472.1
Manufacturing
Segment Reporting Information [Line Items]
Net revenue	147.0	176.9	289.1	334.9
AutoCAD and AutoCAD LT
Segment Reporting Information [Line Items]
Net revenue	96.5	73.1	188.0	159.0
Media and Entertainment
Segment Reporting Information [Line Items]
Net revenue	37.9	34.4	74.4	69.4
Other
Segment Reporting Information [Line Items]
Net revenue	11.6	13.1	22.7	27.2
Americas
Segment Reporting Information [Line Items]
Net revenue	214.0	230.1	424.1	447.8
Americas | U.S.
Segment Reporting Information [Line Items]
Net revenue	184.6	195.2	364.4	379.9
Americas | Other Americas
Segment Reporting Information [Line Items]
Net revenue	29.4	34.9	59.7	67.9
Europe, Middle East and Africa
Segment Reporting Information [Line Items]
Net revenue	199.3	220.5	389.0	423.1
Asia Pacific
Segment Reporting Information [Line Items]
Net revenue	$ 88.5	$ 100.1	$ 174.4	$ 191.7