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Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Millions			12 Months Ended
	Apr. 19, 2017	Apr. 01, 2017	Dec. 31, 2017
Scenario, Forecast | Series A Preferred Stock
Subsequent Event [Line Items]
Anticipated series A preferred stock dividends paid and declared			$ 3.0
Subsequent Event | Common Class A
Subsequent Event [Line Items]
Class A common stock dividends declared (in dollars per share)	$ 0.3625
Subsequent Event | Series A Preferred Stock
Subsequent Event [Line Items]
Series A preferred stock dividend (in dollars per share)	0.72917
Subsequent Event | Scenario, Forecast | Series A Preferred Stock
Subsequent Event [Line Items]
Series A preferred stock dividend (in dollars per share)	1.85
Series A preferred stock dividends declared (in dollars per share)	$ 1.85
National Gas & Electric, LLC | Subsequent Event
Subsequent Event [Line Items]
Payments to Acquire Residential Customer Equivalents		$ 2.2

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- Definition

Payments to Acquire Residential Customer Equivalents

+ References

No definition available.

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- Definition

Aggregate dividends declared during the period for each share of common stock outstanding.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

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- Definition

Amount of paid and unpaid preferred stock dividends declared with the form of settlement in cash.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 405
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6957935&loc=d3e64057-112817

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-Name Accounting Standards Codification
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