Goodwill and Intangible Assets - Definite-Lived Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jul. 31, 2020	Apr. 30, 2020
Definite-lived intangible assets
Gross Carrying Amount	$ 601,825	$ 592,098
Accumulated Amortization	308,650	291,581
Net Carrying Value	$ 293,175	$ 300,517
Customer relationships
Definite-lived intangible assets
Weighted Average Amortization Period (in years)	12 years 9 months 18 days	12 years 9 months 18 days
Gross Carrying Amount	$ 525,304	$ 516,928
Accumulated Amortization	285,000	270,029
Net Carrying Value	$ 240,304	$ 246,899
Customer relationships | Minimum
Definite-lived intangible assets
Estimated Useful Lives (years)	5 years	5 years
Customer relationships | Maximum
Definite-lived intangible assets
Estimated Useful Lives (years)	16 years	16 years
Tradenames
Definite-lived intangible assets
Weighted Average Amortization Period (in years)	16 years 3 months 18 days	16 years 3 months 18 days
Gross Carrying Amount	$ 56,704	$ 55,654
Accumulated Amortization	11,514	10,474
Net Carrying Value	$ 45,190	$ 45,180
Tradenames | Minimum
Definite-lived intangible assets
Estimated Useful Lives (years)	5 years	5 years
Tradenames | Maximum
Definite-lived intangible assets
Estimated Useful Lives (years)	20 years	20 years
Vendor agreements
Definite-lived intangible assets
Weighted Average Amortization Period (in years)	8 years 3 months 18 days	8 years 3 months 18 days
Gross Carrying Amount	$ 6,644	$ 6,644
Accumulated Amortization	4,768	4,567
Net Carrying Value	$ 1,876	$ 2,077
Vendor agreements | Minimum
Definite-lived intangible assets
Estimated Useful Lives (years)	8 years	8 years
Vendor agreements | Maximum
Definite-lived intangible assets
Estimated Useful Lives (years)	10 years	10 years
Developed technology
Definite-lived intangible assets
Estimated Useful Lives (years)	5 years	5 years
Weighted Average Amortization Period (in years)	4 years 10 months 24 days	4 years 10 months 24 days
Gross Carrying Amount	$ 5,218	$ 5,036
Accumulated Amortization	2,300	1,963
Net Carrying Value	$ 2,918	$ 3,073
Leasehold interests
Definite-lived intangible assets
Weighted Average Amortization Period (in years)	7 years 7 months 6 days	7 years 7 months 6 days
Gross Carrying Amount	$ 3,708	$ 3,679
Accumulated Amortization	2,224	2,101
Net Carrying Value	$ 1,484	$ 1,578
Leasehold interests | Minimum
Definite-lived intangible assets
Estimated Useful Lives (years)	1 year	1 year
Leasehold interests | Maximum
Definite-lived intangible assets
Estimated Useful Lives (years)	15 years	15 years
Other intangible assets
Definite-lived intangible assets
Weighted Average Amortization Period (in years)	3 years 4 months 24 days	3 years 4 months 24 days
Gross Carrying Amount	$ 4,247	$ 4,157
Accumulated Amortization	2,844	2,447
Net Carrying Value	$ 1,403	$ 1,710
Other intangible assets | Minimum
Definite-lived intangible assets
Estimated Useful Lives (years)	3 years	3 years
Other intangible assets | Maximum
Definite-lived intangible assets
Estimated Useful Lives (years)	5 years	5 years