Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
REVENUE	$ 102,965	$ 99,086	$ 180,647	$ 174,128
Production Expenses:
Purchased water	26,381	23,712	40,043	39,128
Power	1,493	1,624	2,653	2,892
Groundwater extraction charges	9,100	9,919	15,963	19,451
Other production expenses	5,159	4,626	10,258	8,838
Total production expenses	42,133	39,881	68,917	70,309
Administrative and general	13,408	11,958	25,699	23,526
Maintenance	4,729	4,596	9,054	9,056
Property taxes and other non-income taxes	3,848	3,450	7,976	7,316
Depreciation and amortization	15,101	13,656	30,246	27,239
Merger related expenses	1,775	2,746	4,376	6,552
Total operating expense	80,994	76,287	146,268	143,998
OPERATING INCOME	21,971	22,799	34,379	30,130
OTHER (EXPENSE) INCOME:
Interest on long-term debt and other interest expense	(6,714)	(6,084)	(12,505)	(12,136)
Pension non-service cost	(907)	(595)	(1,828)	(1,178)
Unrealized gain (loss) on California Water Service Group stock	0	140	0	(527)
Interest income on money market fund	2,342	0	4,174	0
Gain on sale of real estate investments	745	0	745	0
Other, net	517	679	907	1,355
Income before income taxes	17,954	16,939	25,872	17,644
Provision for income taxes	4,192	4,068	6,237	3,488
NET INCOME BEFORE NONCONTROLLING INTEREST	13,762	12,871	19,635	14,156
Less net income attributable to the noncontrolling interest	224	0	224	0
SJW GROUP NET INCOME	13,538	12,871	19,411	14,156
SJW GROUP COMPREHENSIVE INCOME	$ 13,538	$ 12,871	$ 19,411	$ 14,156
SJW GROUP EARNINGS PER SHARE
Basic (usd per share)	$ 0.48	$ 0.63	$ 0.68	$ 0.69
Diluted (usd per share)	0.47	0.62	0.68	0.68
DIVIDENDS PER SHARE	$ 0.30	$ 0.28	$ 0.60	$ 0.56
WEIGHTED AVERAGE SHARES OUTSTANDING
Basic (shares)	28,440,221	20,592,014	28,431,764	20,576,757
Diluted (shares)	28,526,022	20,732,127	28,516,927	20,716,665