Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jan. 31, 2018	Apr. 30, 2017	Jan. 31, 2017
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 45,215	$ 55,296	$ 47,731
Allowance for loan losses	0	0	0
Accumulated depreciation and amortization	$ 757,809	$ 678,161	$ 673,594
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	246,198,878
Treasury stock, shares	37,079,700	39,027,573	39,032,420