Revenue Recognition from Contracts with Customers (Schedule of Operating Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Regulated Tariff Sales
Residential	$ 19,788	$ 18,796	$ 53,303	$ 50,979
Commercial	4,418	4,074	11,298	10,521
Industrial	2,868	2,587	7,869	7,165
Fire Protection	3,084	3,010	9,045	8,834
Wholesale	4,319	3,634	11,211	10,265
Non-Regulated Contract Operations	4,203	4,041	11,983	11,452
Total Revenue from Contracts with Customers	38,680	36,142	104,709	99,216
Other Regulated Revenues	151	162	276	260
Other Non-Regulated Revenues	101	90	303	302
Inter-segment Elimination	(219)	(220)	(479)	(459)
Total Revenue	$ 38,713	$ 36,174	$ 104,809	$ 99,319

Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130539-203045

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130545-203045

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130543-203045

Name:	us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration