Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Oct. 31, 2019	Apr. 30, 2019	Oct. 31, 2018
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 65,815	$ 67,228	$ 65,409
Accumulated depreciation and amortization	$ 784,535	$ 745,761	$ 787,978
Common stock, no par value (in usd per share)	$ 0	$ 0	$ 0
Common stock, stated value per share (in usd per share)	$ 0.01	$ 0.01	$ 0.01
Common stock, shares authorized	800,000,000	800,000,000	800,000,000
Common stock, shares issued	231,024,069	238,336,760	242,026,278
Treasury stock, shares	35,778,404	36,377,441	36,499,002