Goodwill and Intangible Assets - Definite-Lived Intangible Assets (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Oct. 31, 2016	Apr. 30, 2016
Definite lived intangible assets
Gross carrying amount	$ 302,787	$ 232,446
Accumulated amortization	92,276	72,024
Net carrying value	$ 210,511	$ 160,422
Customer relationships
Definite lived intangible assets
Weighted average amortization period	11 years	10 years 9 months 18 days
Gross carrying amount	$ 269,967	$ 208,526
Accumulated amortization	89,143	69,929
Net carrying value	$ 180,824	$ 138,597
Customer relationships | Minimum
Definite lived intangible assets
Estimated useful lives	5 years	5 years
Customer relationships | Maximum
Definite lived intangible assets
Estimated useful lives	13 years	13 years
Tradenames
Definite lived intangible assets
Weighted average amortization period	18 years 2 months 12 days	19 years 6 months
Gross carrying amount	$ 24,660	$ 15,760
Accumulated amortization	973	447
Net carrying value	$ 23,687	$ 15,313
Tradenames | Minimum
Definite lived intangible assets
Estimated useful lives	5 years	5 years
Tradenames | Maximum
Definite lived intangible assets
Estimated useful lives	20 years	20 years
Vendor agreement
Definite lived intangible assets
Estimated useful lives	8 years	8 years
Gross carrying amount	$ 5,644	$ 5,644
Accumulated amortization	1,823	1,470
Net carrying value	$ 3,821	$ 4,174
Leasehold interests
Definite lived intangible assets
Weighted average amortization period	8 years 2 months 12 days	8 years 2 months 12 days
Gross carrying amount	$ 2,516	$ 2,516
Accumulated amortization	337	178
Net carrying value	$ 2,179	$ 2,338
Leasehold interests | Minimum
Definite lived intangible assets
Estimated useful lives	7 years	7 years
Leasehold interests | Maximum
Definite lived intangible assets
Estimated useful lives	13 years	13 years
2017 Acquisitions | Customer relationships
Definite lived intangible assets
Definite lived intangible assets	$ 61,400
Weighted average amortization period	11 years 8 months 12 days
2017 Acquisitions | Tradenames
Definite lived intangible assets
Definite lived intangible assets	$ 8,900
Weighted average amortization period	16 years 1 month 6 days