Nature of Business (Details)	Jun. 30, 2018 customer state regulated_distribution_division
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of customers serviced \| customer	3,000,000
Number of regulated distribution divisions \| regulated_distribution_division	6
Number of states with service areas \| state	8

The number of states the entity operates in as of the balance sheet date.

No definition available.

Name:	us-gaap_NumberOfStatesInWhichEntityOperates
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant