Regulatory Matters (Details) $ in Millions	3 Months Ended
Mar. 31, 2018 USD ($)
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 65.8
Public Utilities, Requested Rate Increase (Decrease), Percentage	4.00%
Subsidiaries [Member]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 65.8
Public Utilities, Requested Rate Increase (Decrease), Percentage	4.00%

Percentage of public utility's requested rate increase (decrease) with regulatory agency.

No definition available.

Name:	us-gaap_PublicUtilitiesRequestedRateIncreaseDecreasePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration