Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jan. 31, 2017	Apr. 30, 2016	Jan. 31, 2016
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 47,731	$ 57,011	$ 47,234
Allowance for loan losses	0	5,518	6,931
Accumulated depreciation and amortization	$ 673,594	$ 601,120	$ 585,419
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	260,218,666	264,117,966
Treasury stock, shares	39,032,420	39,701,409	39,712,709