EMPLOYEE BENEFIT PLANS (Tables)

12 Months Ended

Dec. 31, 2016

Compensation and Retirement Disclosure [Abstract]

Schedule of changes in benefit obligations, fair value of plan assets, and funded status of plan

The changes in the benefit obligation, the changes in fair value of plan assets, and the funded status of the Company’s Pension and Post-Retirement Medical Plans as of and for the years ended December 31, 2016 and 2015 were as follows:

	Pension Plans						Post-Retirement Medical Plan
	2016			2015			2016			2015
Change in benefit obligation:
Benefit obligation at beginning of year	$	100,011		$	81,098		$	17,729		$	14,740
Service cost	36,359			24,298			1,047			967
Interest cost	3,096			2,974			528			558
Plan amendments	—			—			2,524			1,533
Benefit payments	(3,449		)	(2,231		)	(575		)	(381		)
Actuarial loss (gain)	(509		)	(6,128		)	1,487			312
Projected benefit obligation at end of year	$	135,508		$	100,011		$	22,740		$	17,729
Change in plan assets:
Fair value of plan assets at beginning of year	$	57,502		$	40,956		$	—		$	—
Actual return on plan assets	3,995			(13		)	—			—
Benefits paid	(3,449		)	(2,231		)	(575		)	(381		)
Employer contributions	17,319			18,790			575			381
Fair value of plan assets at end of year	$	75,367		$	57,502		$	—		$	—
Reconciliation of funded status:
Fair value of plan assets at end of year	$	75,367		$	57,502		$	—		$	—
Less benefit obligations at end of year	135,508			100,011			22,740			17,729
Funded status at end of year	$	(60,141	)	$	(42,509	)	$	(22,740	)	$	(17,729	)

Schedule of expected benefit payments

Benefit payments, which reflect expected future services, that the Company expects to pay are as follows for the years ended December 31:

	Pension Benefits		Post-Retirement Medical Plan
2017	$	12,307	$	1,202
2018	8,873		1,389
2019	11,027		1,653
2020	13,067		1,910
2021	16,079		2,018
Years 2022-2026	114,382		10,438

Schedule of net periodic benefit cost

The components of net periodic benefit cost were as follows for the years ended December 31, 2016, 2015 and 2014:

	Pension Benefits									Post-Retirement Medical Plan
	2016			2015			2014			2016		2015		2014
Components of net period benefit cost:
Service cost	$	36,359		$	24,298		$	19,407		$	1,047	$	967	$	1,099
Interest cost	3,096			2,974			2,404			528		558		520
Expected return on plan assets	(4,681		)	(3,422		)	(2,156		)	—		—		—
Amortization of prior service cost	53			53			39			541		326		258
Amortization of actuarial loss (gain)	1,043			1,228			1,033			—		—		(4		)
Net periodic benefit cost	$	35,870		$	25,131		$	20,727		$	2,116	$	1,851	$	1,873

Schedule of pre-tax amounts recognized in other comprehensive income (loss)

The pre-tax amounts recognized in other comprehensive income (loss) for the years ended December 31, 2016, 2015 and 2014 were as follows:

	Pension Benefits									Post-Retirement Medical Plan
	2016			2015			2014			2016			2015			2014
Prior service costs (credits)	$	—		$	—		$	529		$	2,524		$	1,533		$	3,911
Net actuarial loss (gain)	176			(2,220		)	8,151			1,487			312			1,201
Amortization of losses and prior service cost	(1,096		)	(1,281		)	(1,072		)	(541		)	(326		)	(255		)
Total changes in other comprehensive loss (income)	$	(920	)	$	(3,501	)	$	7,608		$	3,470		$	1,519		$	4,857

Schedule of pre-tax amounts in accumulated other comprehensive loss not yet recognized as components of net periodic costs

The pre-tax amounts in accumulated other comprehensive loss as of December 31, 2016 and 2015 that have not yet been recognized as components of net periodic costs were as follows:

	Pension Benefits						Post-Retirement Medical Plan
	2016			2015			2016			2015
Prior service (costs) credits	$	(476	)	$	(529	)	$	(5,983	)	$	(3,999	)
Net actuarial (loss) gain	(18,975		)	(19,841		)	(1,878		)	(391		)
Total	$	(19,451	)	$	(20,370	)	$	(7,861	)	$	(4,390	)

Schedule of pre-tax amounts in accumulated other comprehensive loss to be recognized over next fiscal year

The following pre-tax amounts included in accumulated other comprehensive loss as of December 31, 2016 are expected to be recognized as components of net period benefit cost during the year ended December 31, 2017:

	Pension Benefits			Post-Retirement Medical Plan
Amortization of prior service (costs) credits	$	(53	)	$	(646	)
Amortization of net actuarial (loss) gain	(452		)	—
Total	$	(505	)	$	(646	)

Schedule of assumptions used

The weighted average assumptions used to determine the net periodic benefit costs for the years ended December 31, 2016, 2015 and 2014 were as follows:

	Qualified Plan						Supplemental Plan						Post-Retirement Medical Plan
	2016		2015		2014		2016		2015		2014		2016		2015		2014
Discount rates:
Effective rate for service cost	4.15	%	4.25	%	4.55	%	4.17	%	4.30	%	4.55	%	4.10	%	4.32	%	4.55	%
Effective rate for interest cost	3.38	%	3.31	%	4.55	%	3.20	%	3.16	%	4.55	%	3.11	%	3.09	%	4.55	%
Effective rate for interest on service cost	3.59	%	3.51	%	4.55	%	3.63	%	3.37	%	4.55	%	3.84	%	4.04	%	4.55	%
Expected long-term rate of return on plan assets	7.00	%	7.00	%	6.70	%	—		—		—		—		—		—
Rate of compensation increase	4.81	%	4.81	%	4.64	%	5.50	%	5.50	%	4.64	%	—		—		—

The weighted average assumptions used to determine the benefit obligations as of December 31, 2016 and 2015 were as follows:

	Qualified Plan				Supplemental Plan				Post-Retirement Medical Plan
	2016		2015		2016		2015		2016		2015
Discount rate - benefit obligations	4.07	%	4.17	%	4.08	%	4.22	%	3.68	%	3.76	%
Rate of compensation increase	4.81	%	4.81	%	5.50	%	5.50	%	—		—

Schedule of assumed health care cost trend rates

The assumed health care cost trend rates as of December 31, 2016 and 2015 were as follows:

	Post-Retirement Medical Plan
	2016		2015
Health care cost trend rate assumed for next year	6.1	%	6.1	%
Rate to which the cost trend rate was assumed to decline (the ultimate trend rate)	4.5	%	4.5	%
Year that the rate reached the ultimate trend rate	2038		2038

Schedule of effect of one-percentage-point change in assumed health care cost trend rates

Assumed health care costs trend rates have a significant effect on the amounts reported for retiree health care plans. A one percentage-point change in assumed health care costs trend rates would have the following effects on the medical post-retirement benefits:

	1% Increase		1% Decrease
Effect on total of service and interest cost components	$	14	$	(13	)
Effect on accumulated post-retirement benefit obligation	388		(367		)

Schedule of fair value of assets of the Company's Qualified Plan

The table below presents the fair values of the assets of the Company’s Qualified Plan as of December 31, 2016 and 2015 by level of fair value hierarchy. Assets categorized in Level 2 of the hierarchy consist of collective trusts and are measured at fair value based on the closing net asset value ("NAV") as determined by the fund manager and reported daily. As noted above, the Company’s post retirement medical plan is funded on a pay-as-you-go basis and has no assets.

	Fair Value Measurements Using NAV as Practical Expedient (Level 2)
	December 31,
	2016		2015
Equities:
Domestic equities	$	23,451	$	17,660
Developed international equities	10,736		8,320
Emerging market equities	5,164		4,017
Global low volatility equities	6,360		4,930
Fixed-income	29,576		22,495
Cash and cash equivalents	80		80
Total	$	75,367	$	57,502