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Subsequent events (Details) - $ / shares	May 09, 2019	Mar. 31, 2019
Subsequent Events [Abstract]
Offer Price By Parent	$ 36	$ 30

Price per share of stock in an outstanding offer by the entity's parent company to purchase all outstanding shares of common stock held by others.

No definition available.

Name:	emci_OfferPriceByParent
Namespace Prefix:	emci_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

No definition available.

Name:	us-gaap_SubsequentEventsAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration