Goodwill and Intangible Assets - Definite-Lived Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jul. 31, 2019	Apr. 30, 2019
Definite-lived intangible assets
Gross Carrying Amount	$ 604,260	$ 596,399
Accumulated Amortization	246,377	228,453
Net Carrying Value	$ 357,883	$ 367,946
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	$ 527,732	$ 520,703
Accumulated Amortization	229,991	214,044
Net Carrying Value	$ 297,741	$ 306,659
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	$ 56,659	$ 56,018
Accumulated Amortization	7,939	6,993
Net Carrying Value	$ 48,720	$ 49,025
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	3,963	3,761
Net Carrying Value	$ 2,681	$ 2,883
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	$ 5,322	$ 5,209
Accumulated Amortization	1,263	971
Net Carrying Value	$ 4,059	$ 4,238
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	$ 3,725	$ 3,707
Accumulated Amortization	1,696	1,502
Net Carrying Value	$ 2,029	$ 2,205
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	$ 4,178	$ 4,118
Accumulated Amortization	1,525	1,182
Net Carrying Value	$ 2,653	$ 2,936
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