Regulatory Decision and Related Accounting and Policy Changes - Additional Information (Details) $ in Thousands		3 Months Ended		9 Months Ended		12 Months Ended
	Jul. 09, 2012 utility	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2019 USD ($)	Mar. 31, 2015 USD ($)
Public Utilities, General Disclosures [Line Items]
Number of utilities to adjust revenue requirement | utility	7
Requested collective rate of increase over revenue	28.00%
Approved collective revenue increase		$ 3,600
Adopted rate of return on common equity		9.50%
Percentage of hook up fee liability to be recorded on ICFA receipts		70.00%
Revenues		$ 10,757	$ 9,942	$ 28,876	$ 26,786
Percentage of deferred revenue to be recorded on ICFA receipts		30.00%
Deferred revenue - ICFA		$ 17,446		17,446			$ 17,372
Percentage reversal of regulatory liability						30.00%
Reversal of regulatory liability						$ 3,400
Regulatory liability		8,331		8,331			8,803
Regulatory assets		1,970		1,970			$ 1,715
ICFA
Public Utilities, General Disclosures [Line Items]
Regulatory liability		7,000		7,000				$ 7,900
Tax Cuts and Jobs Act [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory liability		$ 1,300		$ 1,300