EMPLOYEE BENEFIT PLANS (Tables)

12 Months Ended

Dec. 31, 2018

Retirement Benefits [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, 2018 and 2017 were as follows:

	Pension Plans						Post-Retirement Medical Plan
	2018			2017			2018			2017
Change in benefit obligation:
Benefit obligation at beginning of year	$	185,231		$	135,508		$	21,527		$	22,740
Service cost	47,344			40,572			1,148			1,263
Interest cost	5,793			4,336			620			688
Plan amendments	—			462			—			—
Plan settlements	—			(4,881		)	—			—
Benefit payments	(7,214		)	(4,034		)	(562		)	(693		)
Actuarial (gain) loss	(12,811		)	13,268			(3,388		)	(2,471		)
Projected benefit obligation at end of year	$	218,343		$	185,231		$	19,345		$	21,527
Change in plan assets:
Fair value of plan assets at beginning of year	$	121,652		$	75,367		$	—		$	—
Actual return on plan assets	(6,148		)	14,019			—			—
Benefits paid	(7,214		)	(4,034		)	(562		)	(693		)
Plan settlements	—			(4,881		)	—			—
Employer contributions	35,081			41,181			562			693
Fair value of plan assets at end of year	$	143,371		$	121,652		$	—		$	—
Reconciliation of funded status:
Fair value of plan assets at end of year	$	143,371		$	121,652		$	—		$	—
Less benefit obligations at end of year	218,343			185,231			19,345			21,527
Funded status at end of year	$	(74,972	)	$	(63,579	)	$	(19,345	)	$	(21,527	)

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
2019	$	11,155	$	1,342
2020	13,039		1,605
2021	16,570		1,726
2022	19,991		1,761
2023	19,228		1,746
Years 2024-2028	136,559		9,121

Schedule of net periodic benefit cost

The components of net periodic benefit cost were as follows for the years ended December 31, 2018, 2017 and 2016:

	Pension Benefits									Post-Retirement Medical Plan
	2018			2017			2016			2018		2017		2016
Components of net periodic benefit cost:
Service cost	$	47,344		$	40,572		$	36,359		$	1,148	$	1,263	$	1,047
Interest cost	5,793			4,336			3,096			620		688		528
Expected return on plan assets	(8,540		)	(5,766		)	(4,681		)	—		—		—
Settlement loss recognized	—			993			—			—		—		—
Amortization of prior service cost	85			53			53			646		646		541
Amortization of actuarial loss	285			452			1,043			—		—		—
Net periodic benefit cost	$	44,967		$	40,640		$	35,870		$	2,414	$	2,597	$	2,116

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, 2018, 2017 and 2016 were as follows:

	Pension Benefits									Post-Retirement Medical Plan
	2018			2017			2016			2018			2017			2016
Prior service costs	$	—		$	462		$	—		$	—		$	—		$	2,524
Net actuarial loss (gain)	1,877			5,015			176			(3,388		)	(2,471		)	1,487
Amortization of losses and prior service cost	(826		)	(1,410		)	(1,096		)	(646		)	(646		)	(541		)
Total changes in other comprehensive income (loss)	$	1,051		$	4,067		$	(920	)	$	(4,034	)	$	(3,117	)	$	3,470

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 income (loss) as of December 31, 2018 and 2017 that have not yet been recognized as components of net periodic costs were as follows:

	Pension Benefits						Post-Retirement Medical Plan
	2018			2017			2018			2017
Prior service costs	$	(799	)	$	(885	)	$	(4,691	)	$	(5,337	)
Net actuarial (loss) gain	(24,136		)	(22,544		)	3,981			593
Total	$	(24,935	)	$	(23,429	)	$	(710	)	$	(4,744	)

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 income (loss) as of December 31, 2018 are expected to be recognized as components of net periodic benefit cost during the year ended December 31, 2019:

	Pension Benefits			Post-Retirement Medical Plan
Amortization of prior service costs	$	(86	)	$	(646	)
Amortization of net actuarial (loss) gain	(180		)	135
Total	$	(266	)	$	(511	)

Schedule of assumptions used

The weighted average assumptions used to determine the net periodic benefit costs for the years ended December 31, 2018, 2017 and 2016 were as follows:

	Qualified Plan			Supplemental Plan			Post-Retirement Medical Plan
	2018	2017	2016	2018	2017	2016	2018	2017	2016
Discount rates:
Effective rate for service cost	3.62%	4.15%	4.15%	3.58%	4.17%	4.17%	3.59%	4.10%	4.10%
Effective rate for interest cost	3.21%	3.38%	3.38%	3.15%	3.20%	3.20%	2.97%	3.11%	3.11%
Effective rate for interest on service cost	3.32%	3.59%	3.59%	3.24%	3.63%	3.63%	3.46%	3.84%	3.84%
Expected long-term rate of return on plan assets	6.25%	6.50%	7.00%	N/A	N/A	N/A	N/A	N/A	N/A
Rate of compensation increase	4.53%	4.81%	4.81%	5.00%	5.50%	5.50%	N/A	N/A	N/A

The weighted average assumptions used to determine the benefit obligations as of December 31, 2018 and 2017 were as follows:

	Qualified Plan				Supplemental Plan				Post-Retirement Medical Plan
	2018		2017		2018		2017		2018		2017
Discount rate - benefit obligations	4.22	%	3.58	%	4.17	%	3.55	%	3.99	%	3.33	%
Rate of compensation increase	4.55	%	4.53	%	5.00	%	5.00	%	—		—

Schedule of assumed health care cost trend rates

The assumed health care cost trend rates as of December 31, 2018 and 2017 were as follows:

	Post-Retirement Medical Plan
	2018		2017
Health care cost trend rate assumed for next year	5.8	%	6.0	%
Rate to which the cost trend rate was assumed to decline (the ultimate trend rate)	4.5	%	4.5	%
Year that the rate reaches the ultimate trend rate	2038		2038

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

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

	1% Increase		1% Decrease
Effect on total service and interest cost components	$	11	$	(10	)
Effect on accumulated post-retirement benefit obligation	237		(226		)

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, 2018 and 2017 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,
	2018		2017
Equities:
Domestic equities	$	34,800	$	36,582
Developed international equities	19,201		17,236
Emerging market equities	10,263		8,474
Global low volatility equities	11,437		9,983
Fixed-income	59,680		45,469
Real Estate	7,905		—
Cash and cash equivalents	85		3,908
Total	$	143,371	$	121,652