Goodwill and Intangible Assets - Definite-Lived Intangible Assets (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Jan. 31, 2019	Apr. 30, 2018
Definite-lived intangible assets
Gross Carrying Amount	$ 602,694	$ 318,828
Accumulated Amortization	211,250	157,513
Net Carrying Value	$ 391,444	$ 161,315
Customer relationships
Definite-lived intangible assets
Weighted Average Amortization Period (in years)	12 years 10 months 24 days	10 years 10 months 24 days
Gross Carrying Amount	$ 526,120	$ 282,547
Accumulated Amortization	198,642	150,081
Net Carrying Value	$ 327,478	$ 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)	16 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	$ 56,695	$ 26,250
Accumulated Amortization	6,128	3,578
Net Carrying Value	$ 50,567	$ 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	3,560	2,956
Net Carrying Value	$ 3,084	$ 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	723
Net Carrying Value	$ 4,605
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	1,319	832
Net Carrying Value	$ 2,407	$ 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 4 months 24 days	5 years
Gross Carrying Amount	$ 4,181	$ 521
Accumulated Amortization	878	66
Net Carrying Value	$ 3,303	$ 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