Goodwill and Intangible Assets - Definite-Lived Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jul. 31, 2016	Apr. 30, 2016
Definite lived intangible assets
Gross carrying amount	$ 243,682	$ 232,446
Accumulated amortization	81,456	72,024
Net carrying value	$ 162,226	$ 160,422
Customer relationships
Definite lived intangible assets
Weighted average amortization period	10 years 9 months 18 days	10 years 9 months 18 days
Gross carrying amount	$ 219,362	$ 208,526
Accumulated amortization	78,882	69,929
Net carrying value	$ 140,480	$ 138,597
Customer relationships | Minimum
Definite lived intangible assets
Estimated useful lives	5 years
Customer relationships | Maximum
Definite lived intangible assets
Estimated useful lives	13 years
Tradenames
Definite lived intangible assets
Weighted average amortization period	19 years 2 months 12 days	19 years 6 months
Gross carrying amount	$ 16,160	$ 15,760
Accumulated amortization	670	447
Net carrying value	$ 15,490	15,313
Tradenames | Minimum
Definite lived intangible assets
Estimated useful lives	5 years
Tradenames | Maximum
Definite lived intangible assets
Estimated useful lives	20 years
Vendor agreement
Definite lived intangible assets
Estimated useful lives	8 years
Gross carrying amount	$ 5,644	5,644
Accumulated amortization	1,646	1,470
Net carrying value	$ 3,998	$ 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	258	178
Net carrying value	$ 2,258	$ 2,338
Leasehold interests | Minimum
Definite lived intangible assets
Estimated useful lives	7 years
Leasehold interests | Maximum
Definite lived intangible assets
Estimated useful lives	13 years
2017 Acquisitions | Customer relationships
Definite lived intangible assets
Definite lived intangible assets	$ 10,800
Weighted average amortization period	11 years 7 months 6 days
2017 Acquisitions | Tradenames
Definite lived intangible assets
Definite lived intangible assets	$ 400
Weighted average amortization period	10 years