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Share-based Compensation (Tables) | 9 Months Ended
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Sep. 30, 2021
Share-based Compensation [Abstract] |
Stock Option Activity | ​ The following table is a summary of our stock option activity: ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | Nine months ended September 30,
​ | 2021 | ​ | 2020
​ | Awards | ​ | Weighted-Average Exercise Price | ​ | Awards | ​ | Weighted-Average Exercise Price
(awards in thousands) | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Outstanding at beginning of period | 61 | ​ | $ | 48.19 | ​ | 97 | ​ | $ | 52.53
Exercised | (16) | ​ | ​ | 49.69 | ​ | (24) | ​ | ​ | 58.80
Forfeited | - | ​ | ​ | - | ​ | (6) | ​ | ​ | 68.84
Outstanding at end of the period | 45 | ​ | $ | 47.66 | ​ | 67 | ​ | $ | 48.71
Exercisable at end of the period | 35 | ​ | $ | 42.00 | ​ | 48 | ​ | $ | 40.83
Restricted Stock Activity | The following table summarizes our restricted stock activity:
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | Nine months ended September 30,
​ | 2021 | ​ | 2020
​ | Shares | ​ | Weighted-Average Grant Date Fair Value | ​ | Shares | ​ | Weighted-Average Grant Date Fair Value
(shares in thousands) | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Outstanding at beginning of period | 50 | ​ | $ | 116.06 | ​ | 46 | ​ | $ | 98.28
Granted | 21 | ​ | ​ | 266.99 | ​ | 43 | ​ | ​ | 113.68
Vested | (26) | ​ | ​ | 116.62 | ​ | (30) | ​ | ​ | 86.79
Forfeited | (3) | ​ | ​ | 166.02 | ​ | (7) | ​ | ​ | 108.81
Outstanding at end of the period | 42 | ​ | $ | 183.04 | ​ | 52 | ​ | $ | 116.29

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- Definition Tabular disclosure of the changes in outstanding nonvested restricted stock units. + 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 (c)(2) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Tabular disclosure for stock option plans. Includes, but is not limited to, outstanding awards at beginning and end of year, grants, exercises, forfeitures, and weighted-average grant date fair value. + 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 (d) -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 50 -Paragraph 2 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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