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Share-based Compensation Plans (Tables) | 12 Months Ended
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Dec. 31, 2021
Share-based Payment Arrangement [Abstract] |
Share-based Payment Arrangement, Expensed Amount | Stock-based compensation expense, which is included in Operations and maintenance on the accompanying Consolidated Statements of Income, was as follows for the years ended December 31 (in thousands):
| 2021 | 2020 | 2019
Stock-based compensation expense | $ | 9,655 |  | $ | 5,373 |  | $ | 12,095 |
Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity | A summary of the status of the restricted stock and restricted stock units at December 31, 2021, was as follows:
| Restricted Stock | Weighted-Average Grant Date Fair Value
| (in thousands) |
Balance at January 1, 2021 | 196 |  | $ | 69.05 |
Granted | 118 |  | 65.64 |
Vested | (83) |  | 67.85 |
Forfeited | (12) |  | 69.59 |
Balance at December 31, 2021 | 219 |  | $ | 67.64 |
The weighted-average grant-date fair value of restricted stock granted and the total fair value of shares vested during the years ended December 31, were as follows:
| Weighted-Average Grant Date Fair Value | Total Fair Value of Shares Vested
|  | (in thousands)
2021 | $ | 65.64 |  | $ | 5,400 |
2020 | $ | 69.49 |  | $ | 6,722 |
2019 | $ | 73.66 |  | $ | 8,438 |
Disclosure of Share-based Compensation Arrangements by Share-based Payment Award | The outstanding performance periods at December 31, 2021 were as follows (shares in thousands):
|  |  | Possible Payout Range of Target
Grant Date | Performance Period | Target Grant of Shares | Minimum | Maximum
January 1, 2020 | January 1, 2020 - December 31, 2022 | 36 | 0% | 200%
January 1, 2019 | January 1, 2019 - December 31, 2021 | 36 | 0% | 200%
A summary of the status of the Performance Share Plan at December 31, 2021 was as follows:
| Equity Portion | Liability Portion
|  | Weighted-Average Grant Date Fair Value (a) |  | Weighted-Average Fair Value at
| Shares | Shares | December 31, 2021
| (in thousands) |  | (in thousands) |
Performance Shares balance at beginning of period | 61 |  | $ | 69.71 |  | 61 |  |
Granted | — |  | — |  | — |  |
Forfeited | — |  | — |  | — |  |
Vested | (25) |  | 61.82 |  | (25) |  |
Performance Shares balance at end of period | 36 |  | $ | 68.14 |  | 36 |  | $ | 31.51 |
____________________ (a) The grant date fair values for the performance shares granted in 2020 and 2019 were determined by Monte Carlo simulation using a blended volatility of 18% and 21%, respectively, comprised of 50% historical volatility and 50% implied volatility and the average risk-free interest rate of the three-year United States Treasury security rate in effect as of the grant date. The weighted-average grant-date fair value of performance share awards granted was as follows in the years ended:
| Weighted Average Grant Date Fair Value
December 31, 2020 | $ | 81.42 |
December 31, 2019 | $ | 68.72 |
Performance Plan Payouts | Performance plan payouts have been as follows (in thousands):
Performance Period | Year Paid | Stock Issued | Cash Paid | Total Intrinsic Value
January 1, 2018 to December 31, 2020 | 2021 | 28 |  | $ | 1,647 |  | $ | 3,294 |
January 1, 2017 to December 31, 2019 | 2020 | 14 |  | $ | 1,100 |  | $ | 2,199 |
January 1, 2016 to December 31, 2018 | 2019 | 44 |  | $ | 2,860 |  | $ | 5,720 |
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions | The Monte Carlo simulation is used to estimate expected share payout based on the Company’s TSR for a three-year performance period relative to the designated peer group beginning January 1 of the award year.
| 2021
Fair value of share units award | $64.97
Three-year risk-free rate | 0.17%
Black Hills Corporation’s common stock volatility | 33%
Volatility range for the peer group | 25 | % | - | 76%
Schedule of Nonvested Share Activity | The grant-date fair value for an individual outcome of a performance condition is determined by the closing common share price on the grant date. The following table summarizes the performance share unit activity for the year ended December 31, 2021:
| Performance Share Units - Market Condition | Performance Share Units - Performance Condition
| Share Units | Weighted-Average Fair Value per Share Unit | Share Units | Weighted-Average Fair Value per Share Unit
Nonvested at January 1, 2021 | — |  | $ | — |  | — |  | $ | — |
Granted | 32,903 |  | 64.97 |  | 21,948 |  | 61.45 |
Nonvested at December 31, 2021 | 32,903 |  | $ | 64.97 |  | 21,948 |  | $ | 61.45 |

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- Definition Tabular disclosure of allocation of amount expensed and capitalized for award under share-based payment arrangement to statement of income or comprehensive income and statement of financial position. Includes, but is not limited to, corresponding line item in financial statement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 14.F) -URI http://asc.fasb.org/extlink&oid=122041274&loc=d3e301413-122809 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5047-113901 + Details
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- Definition Tabular disclosure of the significant assumptions used during the year to estimate the fair value of stock options, including, but not limited to: (a) expected term of share options and similar instruments, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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