Acquisitions Narrative (Details)	6 Months Ended
Oct. 31, 2017 store
Business Combinations [Abstract]
Number of stores acquired	14
Goodwill deductible for income tax purposes period (in years)	15 years

The number of businesses acquired by the entity during the period.

No definition available.

Name:	us-gaap_NumberOfBusinessesAcquired
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration