EMPLOYEE BENEFIT PLANS (Tables)

12 Months Ended

Dec. 31, 2016

Compensation and Retirement Disclosure [Abstract]

Disclosures for our Pension Plans and other postretirement benefit plans

The changes in the benefit obligation, the changes in fair value of plan assets, the funded status and the amounts recognized in our consolidated balance sheet for our Pension Plans and other postretirement benefit plans as of and for the year ended December 31, 2015 were as follows:

	Pension Plans			Other Postretirement Benefit Plans
	(Thousands of Dollars)
Change in benefit obligation:
Benefit obligation, January 1	$	106,848		$	10,484
Service cost	7,676			470
Interest cost	4,389			448
Benefits paid	(4,338		)	(507		)
Participant contributions	—			203
Actuarial gain	(5,373		)	(1,056		)
Benefit obligation, December 31	$	109,202		$	10,042
Change in plan assets:
Plan assets at fair value, January 1	$	83,365		$	—
Actual return on plan assets	645			—
Company contributions	8,034			304
Benefits paid	(4,338		)	(507		)
Participant contributions	—			203
Plan assets at fair value, December 31	$	87,706		$	—
Reconciliation of funded status:
Fair value of plan assets at December 31	$	87,706		$	—
Less: Benefit obligation at December 31	109,202			10,042
Funded status at December 31	$	(21,496	)	$	(10,042	)
Amounts recognized in the consolidated balance sheet: (a)
Accrued compensation expense	$	(71	)	$	(304	)
Long-term liabilities	(21,425		)	(9,738		)
Net pension liability	$	(21,496	)	$	(10,042	)

(a) For the Pension Plan, since assets exceeded the present value of expected benefit payments for the following 12 months, all of the liability was noncurrent. For the Excess Pension Plan and the other postretirement benefit plans, since there were no assets, the current liability was the present value of expected benefit payments for the following 12 months; the remainder was noncurrent.

The components of net periodic benefit cost (income)

The components of net periodic benefit cost (income) related to our Pension Plans and other postretirement benefit plans, which were reimbursed to us by NuStar Energy, were as follows:

	Pension Plans						Other Postretirement Benefit Plans
	Year Ended December 31,						Year Ended December 31,
	2015			2014			2015			2014
	(Thousands of Dollars)
Service cost	$	7,676		$	8,049		$	470		$	374
Interest cost	4,389			4,225			448			373
Expected return on plan assets	(5,018		)	(4,574		)	—			—
Amortization of prior service credit	(2,063		)	(2,063		)	(1,145		)	(1,145		)
Amortization of net actuarial loss	1,845			179			269			114
Other	—			(39		)	—			—
Net periodic benefit cost (income)	$	6,829		$	5,777		$	42		$	(284	)

Adjustments recognized in other comprehensive income (loss)

Adjustments recognized in other comprehensive income (loss) related to our Pension Plans and other postretirement benefit plans were as follows:

	Pension Plans						Other Postretirement Benefit Plans
	Year Ended December 31,						Year Ended December 31,
	2015			2014			2015			2014
	(Thousands of Dollars)
Net unrecognized gain (loss) arising during the year:
Net actuarial gain (loss)	$	1,000		$	(14,716	)	$	1,056		$	(2,718	)
Net (gain) loss reclassified into income:
Amortization of prior service credit	(2,063		)	(2,063		)	(1,145		)	(1,145		)
Amortization of net actuarial loss	1,845			179			269			114
Net (gain) loss reclassified into income	(218		)	(1,884		)	(876		)	(1,031		)
Income tax (expense) benefit	(362		)	5,314			(382		)	984
Total changes in other comprehensive income (loss)	$	420		$	(11,286	)	$	(202	)	$	(2,765	)

The amounts recorded as a component of accumulated other comprehensive loss

The amounts recorded as a component of accumulated other comprehensive loss related to our Pension Plans and other postretirement benefit plans were as follows:

	December 31, 2015
	Pension Plans			Other Postretirement Benefit plans
	(Thousands of Dollars)
Unrecognized actuarial loss (a)	$	(21,975	)	$	(3,568	)
Prior service credit (a)	20,727			11,754
Deferred tax asset (liability)	1,313			(3,726		)
Accumulated other comprehensive income, net of tax	$	65		$	4,460

(a) Represents the balance of accumulated other comprehensive income (loss) that has not been recognized as a component of net periodic benefit cost (income).

Schedule of fair value of plan assets

The major classes of plan assets measured at fair value for the Pension Plan were as follows:

	December 31, 2015
	Level 1		Level 2		Level 3		Total
	(Thousands of Dollars)
Cash equivalent securities	$	739	$	—	$	—	$	739
Equity securities:
U.S. large cap equity fund (a)	—		52,086		—		52,086
International stock index fund (b)	8,522		—		—		8,522
Fixed income securities:
Bond market index fund (c)	26,359		—		—		26,359
Total	$	35,620	$	52,086	$	—	$	87,706

(a) This fund is a low-cost equity index fund not actively managed that tracks the S&P 500. Fair values were estimated using pricing models, quoted prices of securities with similar characteristics or discounted cash flows.

(b) This fund tracks the performance of the Total International Composite Index.

(c) This fund tracks the performance of the Barclays Capital U.S. Aggregate Bond Index.

Assumptions used to determine the benefit obligations

The weighted-average assumptions used to determine the benefit obligations were as follows:

	December 31, 2015
	Pension Plans		Other Postretirement Benefit Plans
Discount rate	4.61	%	4.75	%
Rate of compensation increase	3.51	%	n/a

Assumptions used to determine the net periodic benefit cost (income)

The weighted-average assumptions used to determine the net periodic benefit cost (income) were as follows:

	Pension Plans				Other Postretirement Benefit Plans
	Year Ended December 31,				Year Ended December 31,
	2015		2014		2015		2014
Discount rate	4.22	%	5.04	%	4.34	%	5.28	%
Expected long-term rate of return on plan assets	6.50	%	6.75	%	n/a		n/a
Rate of compensation increase	3.51	%	3.51	%	n/a		n/a

Schedule of assumed health care cost trend rates

The assumed health care cost trend rates were as follows:

	December 31, 2015
Health care cost trend rate assumed for 2016	6.81	%
Rate to which the cost trend rate was assumed to decrease to (the ultimate trend rate)	5.00	%
Year that the rate reached the ultimate trend rate	2026