STOCKHOLDERS' EQUITY: Stock-based compensation activity, by award type (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Share-based compensation
Other non-employee stock-based compensation	$ 1.1	$ 1.3	$ 1.0
Total non-cash stock-based compensation	89.4	102.7	52.9
Stock-based compensation of discontinued operations	0.0	62.8	10.3
Total non-cash stock-based compensation included in the consolidated statements of equity	65.2	151.3	61.5
Stock options
Share-based compensation
Share-based compensation expense	3.7	3.3	5.0
Restricted stock units
Share-based compensation
Share-based compensation expense	55.5	67.0	29.1
Arbor Holdback Agreement | Arbor
Share-based compensation
Share-based compensation expense	2.6	15.3	15.3
Consideration Holdback | Data Plus Math Corporation
Share-based compensation
Share-based compensation expense	6.2	0.0	0.0
Pacific Data Partners, LLC Agreement Plan | Pacific Data Partners LLC
Share-based compensation
Share-based compensation expense	20.3	15.8	2.0
Liability-based equity awards
Share-based compensation
Total non-cash stock-based compensation	$ (24.2)	$ (14.2)	$ (1.7)