Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jul. 31, 2017	Apr. 30, 2017	Jul. 31, 2016
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 54,924	$ 55,296	$ 56,381
Allowance for loan losses	0	0	5,310
Accumulated depreciation and amortization	$ 706,687	$ 678,161	$ 622,937
Common stock, no par value	$ 0	$ 0	$ 0
Common stock, stated value 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	246,198,878	246,198,878	258,179,891
Treasury stock, shares	37,141,486	39,027,573	39,087,239