Income Taxes (NOL and Tax Credit Valuation Allowances) (Details) - USD ($) $ in Millions	12 Months Ended
	Jul. 31, 2020	Jul. 31, 2019	Jul. 31, 2018
Valuation Allowance, Deferred Tax Asset
Balance at beginning of year	$ (4.4)	$ (6.2)	$ (5.2)
Additions charged to costs and expenses	(3.7)	(0.2)	(1.0)
Deductions from reserves	0.0	2.0	0.0
Balance at end of year	$ (8.1)	$ (4.4)	$ (6.2)