Description of Business, Basis of Presentation, Corporate Transactions, Significant Accounting Policies, and Recent Accounting Pronouncements - Significant Accounting Policies (10K Only) (Details) - USD ($)	3 Months Ended		12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2016	Dec. 31, 2005	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Amortization of Debt Issuance Costs and Discounts			$ 88,000	$ 101,000
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Outstanding Options	632,500	498,496	632,500	498,496
Revenues			$ 35,471,000	$ 35,515,000		$ 4,900,000
Percentage of hook up fee liability to be recorded on ICFA receipts			70.00%
Restricted cash balances	$ 1,582,000	$ 441,000	$ 1,582,000	441,000
Valuation allowance	$ 0	$ 0	$ 0	$ 0
Number of options outstanding, to acquire shares of GWRI common stock (in shares)	633,000	498,000	633,000	498,000			740,000
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements			14,974	38,928
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options	$ 600,000	$ 14,000	$ 600,000	$ 14,000
Regulatory liability	8,803,000	8,851,000	$ 8,803,000	8,851,000
Percentage of regulatory liability			70.00%
Percentage reversal of regulatory liability					30.00%
Reversal of regulatory liability					$ 3,400,000
AIAC balances	2,900,000	0	$ 2,900,000	0
Refundable AIAC carrying value	67,600,000	67,700,000	67,600,000	67,700,000
Revenue from Contract with Customer, Excluding Assessed Tax	8,685,000	8,253,000	35,471,000	35,515,000
Water [Member]
Property, Plant and Equipment [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	3,799,000	3,570,000	16,143,000	15,344,000
Water [Member] | other water services
Property, Plant and Equipment [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	143,000	148,000	696,000	693,000
connection fees [Member] | other water services
Property, Plant and Equipment [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax			$ 300,000
HUF funds
Property, Plant and Equipment [Line Items]
Restricted cash balances		9,000		$ 9,000
In the Money
Property, Plant and Equipment [Line Items]
Antidilutive securities included in computation of earnings per share (in shares)			386,896	100,000
Out of the Money
Property, Plant and Equipment [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)			245,604	398,496
Certificate of deposits
Property, Plant and Equipment [Line Items]
Restricted cash balances	705,000		$ 705,000
Cash and Cash Equivalents, Fair Value Disclosure	0		0
Fair Value, Inputs, Level 2 [Member] | Certificate of deposits
Property, Plant and Equipment [Line Items]
Restricted cash balances		432,000		$ 432,000
Fair Value, Inputs, Level 2 [Member] | Certificate of deposits | Certificate of deposits
Property, Plant and Equipment [Line Items]
Restricted cash balances		432,000		432,000
Cash and Cash Equivalents, Fair Value Disclosure	705,000		705,000
Fair Value, Inputs, Level 2 [Member] | Certificate of deposits | Payment Guarantee
Property, Plant and Equipment [Line Items]
Restricted cash balances		$ 0		$ 0
Cash and Cash Equivalents, Fair Value Disclosure	$ 250,000		$ 250,000