SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)

12 Months Ended

Dec. 31, 2016

Accounting Policies [Abstract]

Schedule of activities in the allowance for doubtful accounts

The activities in the allowance for doubtful accounts are as follows:

	2016			2015			2014
Beginning Balance	$	730		$	697		$	668
Provision for uncollectible accounts	2,111			1,674			1,561
Net write off of uncollectible accounts	(2,011		)	(1,641		)	(1,532		)
Ending Balance	$	830		$	730		$	697

Schedule of depreciable plant and equipment

The following table represents depreciable plant and equipment as of December 31:

	2016		2015
Equipment	$	561,909	$	499,502
Office buildings and other structures	218,711		198,798
Transmission and distribution plant	1,741,554		1,603,541
Total	$	2,522,174	$	2,301,841

Schedule of estimated useful lives of depreciable plant and equipment

Depreciation of utility plant is computed on a straight-line basis over the assets' estimated useful lives including cost of removal of certain assets as follows:

	Useful Lives
Equipment	5 to 50 years
Transmission and distribution plant	40 to 65 years
Office Buildings and other structures	50 years

Schedule of regulatory assets and liabilities

Regulatory assets and liabilities were comprised of the following as of December 31:

	2016		2015
Regulatory Assets
Pension and retiree group health	$	188,880	$	205,614
Property-related temporary differences (tax benefits flowed through to customers)	92,099		81,522
Other accrued benefits	27,503		27,327
Interim rates long-term accounts receivable	4,605		5,238
Net WRAM and MCBA long-term accounts receivable	16,148		15,410
Asset retirement obligations, net	15,812		14,682
Tank coating	8,452		6,829
Health care balancing account	1,000		3,503
Other regulatory assets	1,431		1,768
Total Regulatory Assets	$	355,930	$	361,893
Regulatory Liabilities
Future tax benefits due customers	$	33,231	$	29,505
Conservation program	584		2,317
Net WRAM and MCBA long-term payable	611		488
Pension balancing account	695		792
Other liabilities	3,614		2,162
Total Regulatory Liabilities	$	38,735	$	35,264

Schedule of SARs which were dilutive

All SARs were dilutive in 2016, 2015 and 2014. The dilutive effect is shown in the table below:

	2016		2015		2014
	(In thousands, except per share data)
Net income available to common stockholders	$	48,675	$	45,017	$	56,738
Weighted average common shares, basic	47,953		47,865		47,791
Dilutive SARs (treasury method)	3		15		38
Weighted average common shares, dilutive	47,956		47,880		47,829
Earnings per share—basic	$	1.02	$	0.94	$	1.19
Earnings per share—diluted	$	1.01	$	0.94	$	1.19

Schedule of accounting change

The following table shows the effect of the accounting change to the consolidated balance sheet as of December 31, 2015:

	December 31, 2015
Balance Sheet Classification	As Reported on Form 10-K		Adjusted Balance on Form 10-K		Decrease from Retrospective Adoption
Other Assets	$	52,241	$	47,399	$	4,842
Long-term debt, less current maturities	512,287		508,002		4,285
Current maturities of long-term debt	6,600		6,043		557