Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
REVENUE	$ 147,209	$ 102,965	$ 262,963	$ 180,647
Production Expenses:
Purchased water	25,889	26,381	41,823	40,043
Power	3,426	1,493	6,151	2,653
Groundwater extraction charges	18,583	9,100	33,611	15,963
Other production expenses	10,280	5,159	20,373	10,258
Total production expenses	58,178	42,133	101,958	68,917
Administrative and general	17,772	13,408	39,388	25,699
Maintenance	5,334	4,729	11,420	9,054
Property taxes and other non-income taxes	7,102	3,848	14,565	7,976
Depreciation and amortization	22,753	15,101	44,135	30,246
Merger related expenses	0	1,775	0	4,376
Total operating expense	111,139	80,994	211,466	146,268
OPERATING INCOME	36,070	21,971	51,497	34,379
OTHER (EXPENSE) INCOME:
Interest on long-term debt and other interest expense	(13,180)	(6,714)	(26,464)	(12,505)
Pension non-service cost	(7)	(907)	(52)	(1,828)
Interest income on money market fund	0	2,342	0	4,174
Gain on sale of real estate investments	0	745	0	745
Other, net	1,048	517	1,805	907
Income before income taxes	23,931	17,954	26,786	25,872
Provision for income taxes	4,210	4,192	4,648	6,237
NET INCOME BEFORE NONCONTROLLING INTEREST	19,721	13,762	22,138	19,635
Less net income attributable to the noncontrolling interest	0	224	0	224
SJW GROUP NET INCOME	19,721	13,538	22,138	19,411
Other comprehensive income (loss), net	10	0	(125)	0
SJW GROUP COMPREHENSIVE INCOME	$ 19,731	$ 13,538	$ 22,013	$ 19,411
SJW GROUP EARNINGS PER SHARE
Basic (usd per share)	$ 0.69	$ 0.48	$ 0.78	$ 0.68
Diluted (usd per share)	0.69	0.47	0.77	0.68
DIVIDENDS PER SHARE	$ 0.32	$ 0.30	$ 0.64	$ 0.60
WEIGHTED AVERAGE SHARES OUTSTANDING
Basic (shares)	28,507,940	28,440,221	28,498,649	28,431,764
Diluted (shares)	28,683,208	28,526,022	28,678,715	28,516,927