EMPLOYEE BENEFIT PLANS (Tables)

12 Months Ended

Dec. 31, 2014

EMPLOYEE BENEFIT PLANS

Summary of target asset allocation percentages for major categories of the pension plan

	Minimum Exposure			Target			Maximum Exposure
Fixed Income		35	%		40	%		45	%
Total Domestic Equity		40	%		50	%		60	%
Small Cap Stocks		10	%		15	%		20	%
Large Cap Stocks		30	%		35	%		45	%
Non-U.S. Equities		5	%		10	%		15	%

Schedule of fair value plan assets

	Pension Benefits										Other Benefits
	2014		%			2013		%			2014		%			2013		%
Fixed Income	$	119,814		39	%	$	102,288		38	%	$	36,313		61	%	$	31,019		62	%
Domestic Equity
Small Cap Stocks		47,798					40,757					—					—
Large Cap Stocks		108,163					96,512					23,528					18,920
Total Domestic Equity		155,961		51	%		137,269		52	%		23,528		39	%		18,920		38	%
Non U.S. Equities		30,569		10	%		26,621		10	%		—		0	%		—		0	%
Total Plan Assets	$	306,344		100	%	$	266,178		100	%	$	59,841		100	%	$	49,939		100	%

Schedule of reconciliation of the funded status of the plans with the accrued pension liability and the net postretirement benefit liability

	Pension Benefits						Other Benefits
	2014			2013			2014			2013
Change in projected benefit obligation:
Beginning of year	$	383,198		$	402,121		$	79,066		$	84,421
Service cost		15,964			17,780			5,205			5,374
Interest cost		18,920			16,354			4,455			3,556
Assumption change		89,692			(53,887	)		37,021			(14,366	)
Experience loss		2,158			6,021			11,020			1,455
Benefits paid, net of retiree premiums		(7,347	)		(5,191	)		(1,534	)		(1,374	)
End of year	$	502,585		$	383,198		$	135,233		$	79,066
Change in plan assets:
Fair value of plan assets at beginning of year	$	266,178		$	202,947		$	49,939		$	37,408
Actual return on plan assets		19,374			36,637			2,376			4,270
Employer contributions		28,139			31,785			9,060			9,635
Retiree contributions and Medicare part D subsidies		—			—			1,535			1,299
Benefits paid		(7,347	)		(5,191	)		(3,069	)		(2,673	)
Fair value of plan assets at end of year	$	306,344		$	266,178		$	59,841		$	49,939
Funded status(1)	$	(196,241	)	$	(117,020	)	$	(75,392	)	$	(29,127	)
Unrecognized actuarial loss		138,609			53,882			70,279			23,311
Unrecognized prior service cost		30,390			36,116			295			340
Unrecognized transition obligation		—			—			—			—
Net amount recognized	$	(27,242	)	$	(27,022	)	$	(4,818	)	$	(5,476	)

(1) The short-term portion of the pension benefits was $1,786 and $1,751 as of December 31, 2014 and 2013, respectively.

Schedule of amounts recognized in consolidated balance sheets

	Pension Benefits						Other Benefits
	2014			2013			2014			2013
(Accrued) benefit costs	$	—		$	—		$	(5,476	)	$	(6,219	)
Accrued benefit liability		(196,241	)		(117,020	)		(75,392	)		(29,127	)
Regulatory asset		168,999			89,998			76,050			29,870
Net amount recognized	$	(27,242	)	$	(27,022	)	$	(4,818	)	$	(5,476	)

Schedule of actuarial assumptions used in determining the benefit obligation

	Pension Benefits						Other Benefits
	2014			2013			2014			2013
Weighted average assumptions as of December 31:
Discount rate		4.00	%		5.00	%		4.00	%		5.00	%
Long-term rate of return on plan assets		6.50	%		6.75	%		5.50	%		6.00	%
Rate of compensation increases		3.25	%		4.00	%		—			—
Cost of living adjustment		2.50	%		3.00	%		—			—

Schedule of sensitivity of pension amounts to changes in actuarial assumptions

	Increase/(Decrease) in Pension Actuarial Assumption			Increase/(Decrease) in 2014 Net Periodic Pension Benefit Cost			Increase/(Decrease) in Projected Pension Benefit Obligation as of December 31, 2014
Discount rate		(0.5	)%	$	4,426		$	53,420
Long-term rate of return on plan assets		(0.5	)%		1,230			—
Rate of compensation increases		(0.5	)%		(2,016	)		(13,522	)
Cost of living adjustment		(0.5	)%		(3,461	)		(33,374	)
Discount rate		0.5	%		(3,938	)		(46,318	)
Long-term rate of return on plan assets		0.5	%		(1,229	)		—
Rate of compensation increases		0.5	%		2,176			14,539

Schedule of components of net periodic benefit costs for the pension plans and other postretirement benefits

	Pension Plan									Other Benefits
	2014			2013			2012			2014			2013			2012
Service cost	$	15,964		$	17,780		$	15,450		$	5,205		$	5,374		$	4,399
Interest cost		18,920			16,354			15,287			4,455			3,556			3,139
Expected return on plan assets		(16,599	)		(14,252	)		(11,558	)		(3,119	)		(2,394	)		(1,832	)
Net amortization and deferral		10,074			15,302			14,283			1,861			2,441			2,425
Net periodic benefit cost	$	28,359		$	35,184		$	33,462		$	8,402		$	8,977		$	8,131

Schedule of actuarial assumptions used in determining the net periodic benefit costs

	Pension Benefits						Other Benefits
	2014			2013			2014			2013
Weighted average assumptions as of December 31:
Discount rate		5.00	%		4.10	%		5.00	%		4.20	%
Long-term rate of return on plan assets		6.75	%		7.00	%		6.00	%		6.00	%
Rate of compensation increases		4.00	%		3.50	%		—			—

Schedule of the effect of a one-percentage point change in assumed health care cost trends

	1-Percentage Point Increase		1-Percentage Point (Decrease)
Effect on total service and interest costs	$	2,633	$	(1,950	)
Effect on accumulated postretirement benefit obligation	$	37,120	$	(27,219	)