Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Apr. 30, 2020	Jan. 31, 2020	Oct. 31, 2019	Jul. 31, 2019	Apr. 30, 2019	Jan. 31, 2019	Oct. 31, 2018	Jul. 31, 2018	Apr. 30, 2020		Apr. 30, 2019		Apr. 30, 2018
Selected Quarterly Financial Data (Unaudited)
Net sales	$ 770,850	$ 761,352	$ 861,929	$ 847,176	$ 780,149	$ 723,902	$ 833,837	$ 778,144	$ 3,241,307		$ 3,116,032		$ 2,511,469
Gross Profit	251,594	253,473	284,493	273,654	256,927	234,226	268,150	244,816	1,063,214		1,004,119		818,576
Net income (loss)	$ (41,456)	$ 10,879	$ 29,138	$ 24,820	$ 16,625	$ 5,815	$ 24,912	$ 8,650	$ 23,381		$ 56,002		$ 62,971
Weighted average shares outstanding:
Basic (in shares)	42,435	42,223	41,761	41,001	40,487	40,912	41,149	41,094	41,853		40,914		41,015
Diluted (in shares)	42,435	42,949	42,635	41,615	40,976	41,371	41,918	42,074	42,504		41,589		42,163
Net income per share:
Basic (in dollars per share)	$ (0.98)	$ 0.26	$ 0.70	$ 0.60	$ 0.40	$ 0.14	$ 0.59	$ 0.21	$ 0.56	[1]	$ 1.33	[1]	$ 1.54	[1]
Diluted (in dollars per share)	$ (0.98)	$ 0.25	$ 0.68	$ 0.59	$ 0.39	$ 0.14	$ 0.58	$ 0.20	$ 0.55	[1]	$ 1.31	[1]	$ 1.49	[1]
Impairment of goodwill	$ 63,100								$ 63,074
Gain on legal settlement	$ 14,000								$ 14,029
Change in fair value of financial instruments								$ (5,700)			$ (6,395)		$ (6,125)

[1] See Note 19 for detailed calculations.