Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2020

Retirement Benefits [Abstract]

Schedule of Defined Benefit Plans Disclosures

The changes in the projected benefit obligation and the fair value of plan assets of our Benefit Plans for the years ended December 31, 2020 and 2019 were as follows (in thousands):

	2020		2019
Changes in projected benefit obligation:
Projected benefit obligation as of the beginning of the period	$	52,142	$	27,539
Acquired	—		16,831
Service cost	1,347		910
Interest cost	1,642		1,794
Actuarial loss (1)	7,038		6,688
Benefits paid	(1,690)		(1,620)
Projected benefit obligation as of the end of the period	$	60,479	$	52,142
Changes in fair value of plan assets:
Fair value of plan assets as of the beginning of the period	$	42,866	$	20,254
Acquired	—		16,027
Actual return (loss) on plan assets	4,860		6,405
Employer contributions	125		1,800
Benefits paid	(1,690)		(1,620)
Fair value of plan assets as of the end of the period	$	46,161	$	42,866

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(1)For the year ended December 31, 2020, the change in the actuarial loss was due to a decrease in the discount rate, new entrants to the plan, and salary changes, partially offset by demographic assumption changes. For the year ended December 31, 2019, the change in the actuarial loss was due to a decrease in the discount rate, partially offset by differences between actual activity and actuarial assumptions and demographic assumption changes.

Schedule of Accumulated and Projected Benefit Obligations

The reconciliation of the underfunded status of our Benefit Plans of December 31, 2020 and 2019 was as follows:

	2020		2019
Projected benefit obligation	$	60,479	$	52,142
Fair value of plan assets	46,161		42,866
Underfunded status	$	14,318	$	9,276
Gross amounts recognized in accumulated other comprehensive income (loss): (1)
Net actuarial gain (loss)	$	(6,946)	$	(2,622)

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(1)As of December 31, 2020, we had no service costs recognized in accumulated other comprehensive income.

Schedule of Assumptions Used

Weighted-average assumptions used to measure our projected benefit obligation as of December 31, 2020, 2019, and 2018 and net periodic benefit costs for the years ended December 31, 2020, 2019 and 2018 are as follows:

	2020		2019		2018
Projected benefit obligation:
Wyoming Refining plan
Discount rate (1)	2.65	%	3.30	%	4.20	%
Rate of compensation increase	3.00	%	3.00	%	3.00	%
U.S. Oil plan
Discount rate (1)	2.35	%	3.10	%	—	%
Rate of compensation increase	3.00	%	3.00	%	—	%
Net periodic benefit costs:
Wyoming Refining plan
Discount rate (1)	3.30	%	4.20	%	3.65	%
Expected long-term rate of return (2)	6.25	%	6.50	%	6.50	%
Rate of compensation increase	3.00	%	3.00	%	3.00	%
U.S. Oil plan
Discount rate (1)	3.10	%	4.10	%	—	%
Expected long-term rate of return (2)	6.00	%	6.00	%	—	%
Rate of compensation increase	3.00	%	3.00	%	—	%

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(1)In determining the discount rate, we use pricing and yield information for high-quality corporate bonds that result in payments similar to the estimated distributions of benefits from our plans.

(2)The expected long-term rate of return is based on the target asset allocation of each plan and capital market assumptions developed using forward-looking models and historical market data and trends.

Schedule of Net Benefit Costs

The net periodic benefit cost for the years ended December 31, 2020, 2019, and 2018 includes the following components:

	2020		2019		2018
Components of net periodic benefit cost:
Service cost	$	1,347	$	910	$	548
Interest cost	1,642		1,794		1,107
Expected return on plan assets	(2,323)		(1,972)		(1,258)
Amortization of net loss	176		95		—
Amortization of prior service cost	1		3		—
Net periodic benefit cost	$	843	$	830	$	397

Schedule of Allocation of Plan Assets

The weighted-average asset allocation for our Wyoming Refining plan at December 31, 2020 is as follows:

	Target		Actual
Asset category:
Equity securities	54	%	54	%
Debt securities	35	%	35	%
Real estate	11	%	11	%
Total	100	%	100	%

    The weighted-average asset allocation for our U.S. Oil plan at December 31, 2020 is as follows:

	Target		Actual
Asset category:
Equity securities	56	%	59	%
Debt securities	43	%	41	%
Cash and Cash Equivalents	1	%	—	%
Total	100	%	100	%

Schedule of Expected Benefit Payments

Based on current data and assumptions, the following benefit payments, which reflect expected future service, as appropriate, are expected to be paid over the next 10 years:

Year Ended
2021	$	2,012
2022	2,098
2023	2,229
2024	2,260
2025	2,468
Thereafter	13,806
	$	24,873