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Employee Benefit Plans (Tables) | 12 Months Ended
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Dec. 31, 2021
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:
| 2021 | 2020
Equity | 15% | 21%
Real estate | 7 | 3
Fixed income | 74 | 69
Cash | 1 | 3
Hedge funds | 3 | 4
Total | 100% | 100%
Schedule of Employer Contribution to Employee Benefit Plans | Contributions for the years ended December 31 were as follows (in thousands):
| 2021 | 2020
Defined Contribution Plan |  |
Company retirement contributions | $ | 11,332 |  | $ | 10,455 |
Company matching contributions | $ | 15,938 |  | $ | 15,240 |
| 2021 | 2020
Defined Benefit Plans |  |
Defined Benefit Pension Plan | $ | — |  | $ | 12,700 |
Non-Pension Defined Benefit Postretirement Healthcare Plan | $ | 6,432 |  | $ | 6,058 |
Supplemental Non-Qualified Defined Benefit Plans | $ | 2,576 |  | $ | 2,674 |
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, | 2021 | 2020 |  | 2021 | 2020 |  | 2021 | 2020
Change in benefit obligation: |  |  |  |  |  |  |  |
Projected benefit obligation at beginning of year | $ | 514,008 |  | $ | 485,376 |  |  | $ | 55,054 |  | $ | 54,088 |  |  | $ | 70,238 |  | $ | 65,277 |
Service cost (a) | 5,038 |  | 5,411 |  |  | 3,149 |  | 1,579 |  |  | 2,237 |  | 2,056 |
Interest cost | 9,313 |  | 13,426 |  |  | 706 |  | 1,099 |  |  | 1,058 |  | 1,649 |
Actuarial (gain) loss | (14,037) |  | 47,064 |  |  | (1,073) |  | 962 |  |  | (5,165) |  | 5,804 |
Amendments | (561) |  | — |  |  | — |  | — |  |  | — |  | — |
Benefits paid | (35,499) |  | (37,269) |  |  | (2,576) |  | (2,674) |  |  | (6,432) |  | (6,058) |
Plan participants’ contributions | — |  | — |  |  | — |  | — |  |  | 1,548 |  | 1,510 |
Projected benefit obligation at end of year | $ | 478,262 |  | $ | 514,008 |  |  | $ | 55,260 |  | $ | 55,054 |  |  | $ | 63,484 |  | $ | 70,238 |
____________________ (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.
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, | 2021 | 2020 |  | 2021 | 2020 |  | 2021 | 2020
Change in fair value of plan assets: |  |  |  |  |  |  |  |
Beginning fair value of plan assets | $ | 473,721 |  | $ | 434,284 |  |  | $ | — |  | $ | — |  |  | $ | 8,165 |  | $ | 8,305 |
Investment income (loss) | 20,165 |  | 64,006 |  |  | — |  | — |  |  | (35) |  | 33 |
Employer contributions | — |  | 12,700 |  |  | 2,576 |  | 2,674 |  |  | 4,726 |  | 4,374 |
Retiree contributions | — |  | — |  |  | — |  | — |  |  | 1,548 |  | 1,511 |
Benefits paid | (35,499) |  | (37,269) |  |  | (2,576) |  | (2,674) |  |  | (6,432) |  | (6,058) |
Ending fair value of plan assets | $ | 458,387 |  | $ | 473,721 |  |  | $ | — |  | $ | — |  |  | $ | 7,972 |  | $ | 8,165 |
____________________ (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, | 2021 | 2020 |  | 2021 | 2020 |  | 2021 | 2020
Regulatory assets | $ | 67,403 |  | $ | 86,677 |  |  | $ | — |  | $ | — |  |  | $ | 11,660 |  | $ | 16,102 |
Current liabilities | $ | — |  | $ | — |  |  | $ | 2,156 |  | $ | 1,927 |  |  | $ | 4,584 |  | $ | 4,931 |
Non-current liabilities | $ | 19,872 |  | $ | 40,287 |  |  | $ | 53,104 |  | $ | 53,127 |  |  | $ | 50,949 |  | $ | 57,142 |
Regulatory liabilities | $ | 3,830 |  | $ | 3,607 |  |  | $ | — |  | $ | — |  |  | $ | 2,447 |  | $ | 2,140 |
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, | 2021 | 2020 |  | 2021 | 2020 |  | 2021 | 2020
Accumulated Benefit Obligation | $ | 466,505 |  | $ | 498,815 |  |  | $ | 55,260 |  | $ | 54,779 |  |  | $ | 63,484 |  | $ | 70,238 |
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, | 2021 | 2020 | 2019 |  | 2021 | 2020 | 2019 |  | 2021 | 2020 | 2019
Service cost (a) | $ | 5,038 |  | $ | 5,411 |  | $ | 5,383 |  |  | $ | 3,149 |  | $ | 1,579 |  | $ | 4,995 |  |  | $ | 2,237 |  | $ | 2,056 |  | $ | 1,815 |
Interest cost | 9,313 |  | 13,426 |  | 17,374 |  |  | 706 |  | 1,099 |  | 1,295 |  |  | 1,058 |  | 1,649 |  | 2,247 |
Expected return on assets | (20,876) |  | (22,591) |  | (24,401) |  |  | — |  | — |  | — |  |  | (136) |  | (182) |  | (230) |
Net amortization of prior service cost | — |  | — |  | 26 |  |  | — |  | 2 |  | 2 |  |  | (434) |  | (546) |  | (398) |
Recognized net actuarial loss (gain) | 7,315 |  | 8,372 |  | 3,763 |  |  | 1,754 |  | 1,702 |  | 535 |  |  | 466 |  | 20 |  | — |
Net periodic expense | $ | 790 |  | $ | 4,618 |  | $ | 2,145 |  |  | $ | 5,609 |  | $ | 4,382 |  | $ | 6,827 |  |  | $ | 3,191 |  | $ | 2,997 |  | $ | 3,434 |
____________________ (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.
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, | 2021 | 2020 |  | 2021 | 2020 |  | 2021 | 2020
Net (gain) loss | $ | 4,398 |  | $ | 5,511 |  |  | $ | 7,159 |  | $ | 9,323 |  |  | $ | (308) |  | $ | 100 |
Prior service cost (gain) | (46) |  | — |  |  | — |  | — |  |  | (27) |  | (144) |
Total amounts included in AOCI, after-tax not yet recognized as components of net periodic expense | $ | 4,352 |  | $ | 5,511 |  |  | $ | 7,159 |  | $ | 9,323 |  |  | $ | (335) |  | $ | (44) |
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: | 2021 | 2020 | 2019 |  | 2021 | 2020 | 2019 |  | 2021 | 2020 | 2019
Discount rate | 2.88 | % | 2.56 | % | 3.27 | % |  | 2.77 | % | 2.41 | % | 3.14 | % |  | 2.79 | % | 2.41 | % | 3.15 | %
Rate of increase in compensation levels | 3.08 | % | 3.34 | % | 3.49 | % |  | 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: | 2021 | 2020 | 2019 |  | 2021 | 2020 | 2019 |  | 2021 | 2020 | 2019
Discount rate (a) | 2.56 | % | 3.27 | % | 4.40 | % |  | 2.41 | % | 3.14 | % | 4.34 | % |  | 2.41 | % | 3.15 | % | 4.28 | %
Expected long-term rate of return on assets (b) | 4.50 | % | 5.25 | % | 6.00 | % |  | N/A | N/A | N/A |  | 1.80 | % | 2.35 | % | 3.00 | %
Rate of increase in compensation levels | 3.34 | % | 3.49 | % | 3.52 | % |  | 5.00 | % | 5.00 | % | 5.00 | % |  | N/A | N/A | N/A
____________________ (a) The estimated discount rate for the Defined Benefit Pension Plan is 2.88% for the calculation of the 2022 net periodic pension costs. (b) The expected rate of return on plan assets is 4.25% for the calculation of the 2022 net periodic pension cost.
Schedule of Health Care Cost Trend Rates | The healthcare benefit obligation at December 31 was determined as follows:
| 2021 | 2020
Trend Rate - Medical |  |
Pre-65 for next year - All Plans | 6.05% | 6.10%
Pre-65 Ultimate trend rate - Black Hills Corp | 4.50% | 4.50%
Trend Year | 2030 | 2027
Post-65 for next year - All Plans | 5.10% | 4.92%
Post-65 Ultimate trend rate - Black Hills Corp | 4.50% | 4.50%
Trend Year | 2030 | 2029
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
2022 | $ | 26,249 |  |  | $ | 2,156 |  |  | $ | 5,806 |
2023 | $ | 27,133 |  |  | $ | 2,224 |  |  | $ | 5,334 |
2024 | $ | 27,683 |  |  | $ | 2,410 |  |  | $ | 5,042 |
2025 | $ | 28,650 |  |  | $ | 2,757 |  |  | $ | 4,865 |
2026 | $ | 28,968 |  |  | $ | 2,782 |  |  | $ | 4,752 |
2027-2031 | $ | 144,422 |  |  | $ | 12,553 |  |  | $ | 21,615 |
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, 2021
| Level 1 |  | Level 2 |  | Level 3 |  | Total Investments Measured at Fair Value |  | NAV (a) |  | Total Investments
Common Collective Trust - Cash and Cash Equivalents | $ | — |  |  | $ | 6,009 |  |  | $ | — |  |  | $ | 6,009 |  |  | $ | — |  |  | $ | 6,009 |
Common Collective Trust - Equity | — |  |  | 70,262 |  |  | — |  |  | 70,262 |  |  | — |  |  | 70,262 |
Common Collective Trust - Fixed Income | — |  |  | 339,219 |  |  | — |  |  | 339,219 |  |  | — |  |  | 339,219 |
Common Collective Trust - Real Estate | — |  |  | — |  |  | — |  |  | — |  |  | 30,407 |  |  | 30,407 |
Hedge Funds | — |  |  | — |  |  | — |  |  | — |  |  | 12,490 |  |  | 12,490 |
Total investments measured at fair value | $ | — |  |  | $ | 415,490 |  |  | $ | — |  |  | $ | 415,490 |  |  | $ | 42,897 |  |  | $ | 458,387 |
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 |
____________________ (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, 2021
| Level 1 |  | Level 2 |  | Level 3 |  | Total Investments Measured at Fair Value |  |  |  | Total Investments
Cash and Cash Equivalents | $ | 7,972 |  |  | $ | — |  |  | $ | — |  |  | $ | 7,972 |  |  |  |  | $ | 7,972 |
Total investments measured at fair value | $ | 7,972 |  |  | $ | — |  |  | $ | — |  |  | $ | 7,972 |  |  |  |  | $ | 7,972 |
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 |

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