Revenue Recognition Contract Revenue (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Jan. 31, 2021	Oct. 31, 2020	Jul. 31, 2020	Apr. 30, 2020	Jan. 31, 2020	Oct. 31, 2019	Jul. 31, 2019	Apr. 30, 2019	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2019
Disaggregation of Revenue [Line Items]
Net revenue	$ 1,039.2	$ 952.4	$ 913.1	$ 885.7	$ 899.3	$ 842.7	$ 796.8	$ 735.5	$ 3,790.4	$ 3,274.3	$ 2,569.8
Indirect
Disaggregation of Revenue [Line Items]
Net revenue									2,600.0	2,282.2	1,830.8
Direct
Disaggregation of Revenue [Line Items]
Net revenue									1,190.4	992.1	739.0
Americas
Disaggregation of Revenue [Line Items]
Net revenue									1,542.4	1,335.8	1,049.9
U.S.
Disaggregation of Revenue [Line Items]
Net revenue									1,281.8	1,108.9	874.6
Other Americas
Disaggregation of Revenue [Line Items]
Net revenue									260.6	226.9	175.3
Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Net revenue									1,472.6	1,303.5	1,034.3
Asia Pacific
Disaggregation of Revenue [Line Items]
Net revenue									775.4	635.0	485.6
Architecture, Engineering and Construction
Disaggregation of Revenue [Line Items]
Net revenue									1,648.6	1,377.1	1,021.6
Manufacturing
Disaggregation of Revenue [Line Items]
Net revenue									798.6	726.1	616.2
AutoCAD and AutoCAD LT
Disaggregation of Revenue [Line Items]
Net revenue									1,099.4	948.2	731.8
Media and Entertainment
Disaggregation of Revenue [Line Items]
Net revenue									219.4	199.2	182.0
Other
Disaggregation of Revenue [Line Items]
Net revenue									24.4	23.7	18.2
Design
Disaggregation of Revenue [Line Items]
Net revenue									3,365.8	2,920.1	2,347.8
Make
Disaggregation of Revenue [Line Items]
Net revenue									296.4	218.4	89.6
Other
Disaggregation of Revenue [Line Items]
Net revenue									$ 128.2	$ 135.8	$ 132.4