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Employee Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2020

Defined Benefit Plan Disclosure [Line Items]

Schedule of Allocation of Plan Assets

The percentages of total plan asset by investment category for our Pension Plan at December 31 were as follows:

			2020			2019
Equity			21%			20%
Real estate			3			3
Fixed income			69			71
Cash			3			1
Hedge funds			4			5
Total			100%			100%

Schedule of Employer Contribution to Employee Benefit Plans

Contributions for the years ended December 31 were as follows (in thousands):

			2020			2019
Defined Contribution Plan
Company retirement contributions			$	10,455		$	9,714
Company matching contributions			$	15,240		$	14,558

			2020			2019
Defined Benefit Plans
Defined Benefit Pension Plan			$	12,700		$	12,700
Non-Pension Defined Benefit Postretirement Healthcare Plan			$	6,058		$	7,033
Supplemental Non-Qualified Defined Benefit Plans			$	2,674		$	2,344

Schedule of Changes in Projected Benefit Obligations

The following tables provide a reconciliation of the employee benefit plan obligations and fair value of employee benefit plan assets, amounts recognized in the Consolidated Balance Sheets, accumulated benefit obligation, and reconciliation of components of the net periodic expense and elements of AOCI (in thousands):

Employee Benefit Plan Obligations

			Defined Benefit Pension Plan									Supplemental Non-qualified Defined Benefit Plans									Non-pension Defined Benefit Postretirement Healthcare Plan
As of December 31,			2020			2019						2020			2019						2020			2019
Change in benefit obligation:
Projected benefit obligation at beginning of year			$	485,376		$	445,381					$	54,088		$	43,010					$	65,277		$	60,817
Service cost (a)			5,411			5,383						1,579			4,995						2,056			1,815
Interest cost			13,426			17,374						1,099			1,295						1,649			2,247
Actuarial (gain) loss			47,064			56,384						962			7,132						5,804			5,976
Benefits paid			(37,269)			(39,146)						(2,674)			(2,344)						(6,058)			(7,033)
Plan participants’ contributions			—			—						—			—						1,510			1,455
Projected benefit obligation at end of year			$	514,008		$	485,376					$	55,054		$	54,088					$	70,238		$	65,277

____________________

(a)    For the year ended December 31, 2020, Service Cost for the Supplemental Non-qualified Defined Benefit Plans includes a $1.4 million correction of a prior year overstatement of Projected benefit obligation. Due to the immaterial nature of this correction, the prior year information was not revised.

Schedule of Changes in Fair Value of Plan Assets

			Defined Benefit Pension Plan									Supplemental Non-qualified Defined Benefit Plans									Non-pension Defined Benefit Postretirement Healthcare Plan (a)
As of December 31,			2020			2019						2020			2019						2020			2019
Change in fair value of plan assets:
Beginning fair value of plan assets			$	434,284		$	390,796					$	—		$	—					$	8,305		$	8,162
Investment income (loss)			64,006			69,934						—			—						33			260
Employer contributions			12,700			12,700						2,674			2,344						4,374			5,461
Retiree contributions			—			—						—			—						1,511			1,455
Benefits paid			(37,269)			(39,146)						(2,674)			(2,344)						(6,058)			(7,033)
Ending fair value of plan assets			$	473,721		$	434,284					$	—		$	—					$	8,165		$	8,305

____________________

(a)    Assets of VEBA trusts.

Schedule of Amounts Recognized in Balance Sheet

Amounts Recognized in the Consolidated Balance Sheets

			Defined Benefit Pension Plan									Supplemental Non-qualified Defined Benefit Plans									Non-pension Defined Benefit Postretirement Healthcare Plan
As of December 31,			2020			2019						2020			2019						2020			2019
Regulatory assets			$	86,677		$	88,471					$	—		$	—					$	16,102		$	11,670
Current liabilities			$	—		$	—					$	1,927		$	1,420					$	4,931		$	4,802
Non-current liabilities			$	40,287		$	51,093					$	53,127		$	51,243					$	57,142		$	52,136
Regulatory liabilities			$	3,607		$	3,524					$	—		$	—					$	2,140		$	4,088

Schedule of Accumulated and Projected Benefit Obligations

Accumulated Benefit Obligation

			Defined Benefit Pension Plan									Supplemental Non-qualified Defined Benefit Plans									Non-pension Defined Benefit Postretirement Healthcare Plan
As of December 31,			2020			2019						2020			2019						2020			2019
Accumulated Benefit Obligation			$	498,815		$	470,615					$	54,779		$	49,241					$	70,238		$	65,277

Components of net periodic benefit cost

			Defined Benefit Pension Plan												Supplemental Non-qualified Defined Benefit Plans												Non-pension Defined Benefit Postretirement Healthcare Plan
For the years ended December 31,			2020			2019			2018						2020			2019			2018						2020			2019			2018
Service cost (a)			$	5,411		$	5,383		$	6,834					$	1,579		$	4,995		$	1,764					$	2,056		$	1,815		$	2,291
Interest cost			13,426			17,374			15,470						1,099			1,295			1,170						1,649			2,247			2,085
Expected return on assets			(22,591)			(24,401)			(24,741)						—			—			—						(182)			(230)			(315)
Net amortization of prior service cost			—			26			58						2			2			2						(546)			(398)			(398)
Recognized net actuarial loss (gain)			8,372			3,763			8,632						1,702			535			1,000						20			—			216
Net periodic expense			$	4,618		$	2,145		$	6,253					$	4,382		$	6,827		$	3,936					$	2,997		$	3,434		$	3,879

____________________

(a)    For the year ended December 31, 2020, Service Cost for the Supplemental Non-qualified Defined Benefit Plans includes a $1.4 million correction of a prior year overstatement of Projected benefit obligation. Due to the immaterial nature of this correction, the prior year information was not revised.

Schedule of Net Periodic Benefit Cost Not yet Recognized

			Defined Benefit Pension Plan									Supplemental Non-qualified Defined Benefit Plans									Non-pension Defined Benefit Postretirement Healthcare Plan
As of December 31,			2020			2019						2020			2019						2020			2019
Net (gain) loss			$	5,511		$	5,322					$	9,323		$	9,893					$	100		$	90
Prior service cost (gain)			—			—						—			2						(144)			(230)
Total amounts included in AOCI, after-tax not yet recognized as components of net periodic expense			$	5,511		$	5,322					$	9,323		$	9,895					$	(44)		$	(140)

Schedule of Assumptions Used

Assumptions

			Defined Benefit Pension Plan												Supplemental Non-qualified Defined Benefit Plans												Non-pension Defined Benefit Postretirement Healthcare Plan
Weighted-average assumptions used to determine benefit obligations:			2020			2019			2018						2020			2019			2018						2020			2019			2018
Discount rate			2.56		%	3.27		%	4.40		%				2.41		%	3.14		%	4.34		%				2.41		%	3.15		%	4.28		%
Rate of increase in compensation levels			3.34		%	3.49		%	3.52		%				5.00		%	5.00		%	5.00		%				N/A			N/A			N/A

			Defined Benefit Pension Plan												Supplemental Non-qualified Defined Benefit Plans												Non-pension Defined Benefit Postretirement Healthcare Plan
Weighted-average assumptions used to determine net periodic benefit cost for plan year:			2020			2019			2018						2020			2019			2018						2020			2019			2018
Discount rate (a)			3.27		%	4.40		%	3.71		%				3.14		%	4.34		%	3.67		%				3.15		%	4.28		%	3.60		%
Expected long-term rate of return on assets (b)			5.25		%	6.00		%	6.25		%				N/A			N/A			N/A						2.35		%	3.00		%	3.93		%
Rate of increase in compensation levels			3.49		%	3.52		%	3.43		%				5.00		%	5.00		%	5.00		%				N/A			N/A			N/A

_____________________________

(a)    The estimated discount rate for the Defined Benefit Pension Plan is 2.56% for the calculation of the 2021 net periodic pension costs.

(b)    The expected rate of return on plan assets is 4.50% for the calculation of the 2021 net periodic pension cost.

Schedule of Health Care Cost Trend Rates

The healthcare benefit obligation at December 31 was determined as follows:

			2020			2019
Trend Rate - Medical
Pre-65 for next year - All Plans			6.10%			6.40%
Pre-65 Ultimate trend rate - Black Hills Corp			4.50%			4.50%
Trend Year			2027			2027
Post-65 for next year - All Plans			4.92%			4.92%
Post-65 Ultimate trend rate - Black Hills Corp			4.50%			4.50%
Trend Year			2029			2028

Schedule of Expected Benefit Payments

The following benefit payments to employees, which reflect future service, are expected to be paid (in thousands):

			Defined Benefit Pension Plan						Supplemental Non-qualified Defined Benefit Plans						Non-pension Defined Benefit Postretirement Healthcare Plan
2021			$	25,842					$	1,927					$	6,108
2022			$	26,658					$	1,968					$	5,965
2023			$	27,581					$	2,033					$	5,725
2024			$	28,284					$	2,231					$	5,532
2025			$	29,062					$	2,690					$	5,244
2026-2030			$	144,273					$	13,117					$	22,872

Pension Plan

Defined Benefit Plan Disclosure [Line Items]

Schedule of Allocation of Plan Assets

The following tables set forth, by level within the fair value hierarchy, the assets that were accounted for at fair value on a recurring basis (in thousands):

Pension Plan			December 31, 2020
			Level 1						Level 2						Level 3						Total Investments Measured at Fair Value						NAV (a)						Total Investments
Common Collective Trust - Cash and Cash Equivalents			$	—					$	16,810					$	—					$	16,810					$	—					$	16,810
Common Collective Trust - Equity			—						100,311						—						100,311						—						100,311
Common Collective Trust - Fixed Income			—						324,845						—						324,845						—						324,845
Common Collective Trust - Real Estate			—						—						—						—						14,301						14,301
Hedge Funds			—						—						—						—						17,454						17,454
Total investments measured at fair value			$	—					$	441,966					$	—					$	441,966					$	31,755					$	473,721

Pension Plan			December 31, 2019
			Level 1						Level 2						Level 3						Total Investments Measured at Fair Value						NAV (a)						Total Investments
AXA Equitable General Fixed Income			$	—					$	60					$	—					$	60					$	—					$	60
Common Collective Trust - Cash and Cash Equivalents			—						7,054						—						7,054						—						7,054
Common Collective Trust - Equity			—						87,106						—						87,106						—						87,106
Common Collective Trust - Fixed Income			—						306,275						—						306,275						—						306,275
Common Collective Trust - Real Estate			—						—						—						—						14,239						14,239
Hedge Funds			—						—						—						—						19,550						19,550
Total investments measured at fair value			$	—					$	400,495					$	—					$	400,495					$	33,789					$	434,284

_____________

(a)    Certain investments that are measured at fair value using NAV per share (or its equivalent) for practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in these tables for these investments are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the reconciliation of changes in the plan’s benefit obligations and fair value of plan assets above.

Postretirement Health Coverage

Defined Benefit Plan Disclosure [Line Items]

Schedule of Allocation of Plan Assets

Non-pension Defined Benefit Postretirement Healthcare Plan			December 31, 2020
			Level 1						Level 2						Level 3						Total Investments Measured at Fair Value												Total Investments
Cash and Cash Equivalents			$	8,165					$	—					$	—					$	8,165											$	8,165
Total investments measured at fair value			$	8,165					$	—					$	—					$	8,165											$	8,165

Non-pension Defined Benefit Postretirement Healthcare Plan			December 31, 2019
			Level 1						Level 2						Level 3						Total Investments Measured at Fair Value												Total Investments
Cash and Cash Equivalents			$	8,305					$	—					$	—					$	8,305											$	8,305
Total investments measured at fair value			$	8,305					$	—					$	—					$	8,305											$	8,305

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