Loss Per Share and Stockholders' Equity (Narrative) (Details) - USD ($) shares in Thousands, $ in Millions	3 Months Ended
	Jul. 31, 2019	Jul. 31, 2018
Earnings Per Share [Abstract]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	3,700	3,400
Basic weighted average common shares (in shares)	202,037	207,673
Shares repurchased during the period, (in shares)	300	200
Shares repurchased during the period, value	$ 9.2	$ 4.6
Shares issued during period (in shares)	900	600
Nonvested units granted	1,300
Stock-based compensation	$ 6.7	$ 4.4
Unrecognized compensation costs, options	0.5
Unrecognized compensation costs, nonvested shares and units	$ 55.9