Supplementary Quarterly Financial Information - Results By Quarter (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Apr. 30, 2021		Jan. 31, 2021		Oct. 31, 2020		Jul. 31, 2020		Apr. 30, 2020		Jan. 31, 2020		Oct. 31, 2019		Jul. 31, 2019		Apr. 30, 2021		Apr. 30, 2020		Apr. 30, 2019
Supplementary Quarterly Financial Information - Results By Quarter (Unaudited) [Abstract]
Revenue, net	$ 536,300		$ 482,900		$ 491,000		$ 431,300		$ 474,700		$ 467,100		$ 466,200		$ 423,500		$ 1,941,501		$ 1,831,483		$ 1,800,069
Gross profit	368,200		325,300		336,200		286,500		324,100		313,200		322,800		280,400		1,316,200		1,240,500
Operating income (loss)	51,200		34,400		69,900		30,000		(170,700)		48,500		63,400		4,500		185,511		(54,287)		223,989
Net income (loss)	$ 41,400		$ 22,200		$ 68,400		$ 16,300		$ (158,000)		$ 35,400		$ 44,700		$ 3,600		$ 148,256		$ (74,287)		$ 168,263
Earnings (loss) per share [Abstract]
Basic (in dollars per share)	$ 0.74	[1]	$ 0.40	[1]	$ 1.22	[1]	$ 0.29	[1]	$ (2.83)	[1],[2]	$ 0.63	[1]	$ 0.79	[1]	$ 0.06	[1]	$ 2.65	[1]	$ (1.32)	[1],[2]	$ 2.94
Diluted (in dollars per share)	$ 0.73	[1]	$ 0.39	[1]	$ 1.22	[1]	$ 0.29	[1]	$ (2.83)	[1],[2]	$ 0.63	[1]	$ 0.79	[1]	$ 0.06	[1]	$ 2.63	[1]	$ (1.32)	[1],[2]	$ 2.91

[1] The sum of the quarterly earnings (loss) per share amounts may not agree to the respective annual amounts due to rounding.

[2] In calculating diluted earnings (loss) per common share for the fourth quarter and year ended April 30, 2020, our diluted weighted average number of common shares outstanding excludes the effect of unvested restricted stock units and other stock awards as the effect was anti-dilutive. This occurs when a US GAAP net loss is reported and the effect of using dilutive shares is antidilutive.