Goodwill and Intangible Assets - Definite-Lived Intangible Assets (Details) $ in Thousands	6 Months Ended	12 Months Ended
	Oct. 31, 2018 USD ($) segment	Apr. 30, 2018 USD ($)
Definite-lived intangible assets
Number of operating segments | segment	7
Gross Carrying Amount	$ 604,924	$ 318,828
Accumulated Amortization	192,605	157,513
Net Carrying Value	$ 412,319	$ 161,315
Customer relationships
Definite-lived intangible assets
Weighted Average Amortization Period (in years)	11 years 10 months 24 days	10 years 10 months 24 days
Gross Carrying Amount	$ 529,173	$ 282,547
Accumulated Amortization	181,875	150,081
Net Carrying Value	$ 347,298	$ 132,466
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)	13 years	13 years
Tradenames
Definite-lived intangible assets
Weighted Average Amortization Period (in years)	16 years 3 months 18 days	18 years
Gross Carrying Amount	$ 55,936	$ 26,250
Accumulated Amortization	5,209	3,578
Net Carrying Value	$ 50,727	$ 22,672
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	3,359	2,956
Net Carrying Value	$ 3,285	$ 3,688
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
Weighted Average Amortization Period (in years)	4 years 10 months 24 days
Gross Carrying Amount	$ 5,328
Accumulated Amortization	451
Net Carrying Value	$ 4,877
Leasehold interests
Definite-lived intangible assets
Weighted Average Amortization Period (in years)	7 years 7 months 6 days	9 years
Gross Carrying Amount	$ 3,726	$ 2,866
Accumulated Amortization	1,129	832
Net Carrying Value	$ 2,597	$ 2,034
Leasehold interests | Minimum
Definite-lived intangible assets
Estimated Useful Lives (years)	1 year	7 years
Leasehold interests | Maximum
Definite-lived intangible assets
Estimated Useful Lives (years)	15 years	15 years
Other
Definite-lived intangible assets
Estimated Useful Lives (years)		5 years
Weighted Average Amortization Period (in years)	3 years 3 months 18 days	5 years
Gross Carrying Amount	$ 4,117	$ 521
Accumulated Amortization	582	66
Net Carrying Value	$ 3,535	$ 455
Other | Minimum
Definite-lived intangible assets
Estimated Useful Lives (years)	3 years
Other | Maximum
Definite-lived intangible assets
Estimated Useful Lives (years)	5 years