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Quarterly Financial Data (Unaudited) (Tables) | 12 Months Ended
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Dec. 31, 2020
Quarterly Financial Data (Unaudited) |
Schedule of Quarterly Financial Data (Unaudited) | Unaudited summarized financial data by quarter for 2020 and 2019 is as follows (in thousands, except per share data):
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Year ended December 31, 2020 |
​ | ​ | First | ​ | Second | ​ | Third | ​ | Fourth | ​ | ​ | ​ |
​ | ​ | Quarter | ​ | Quarter | ​ | Quarter | ​ | Quarter | ​ | Year |
Operating revenues |  | $ | 729,936 |  | $ | 350,039 |  | $ | 457,493 |  | $ | 589,638 |  | $ | 2,127,106 | ​
Operating income | ​ |  | 66,321 | ​ |  | (4,403) | ​ |  | 74,553 | ​ |  | (27,669) | ​ |  | 108,802 | ​
Net income | ​ |  | 29,988 | ​ |  | (25,715) | ​ |  | 33,662 | ​ |  | (46,450) | ​ |  | (8,515) | ​
Net income per common share: | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Basic | ​ |  | 0.60 | ​ |  | (0.51) | ​ |  | 0.67 | ​ |  | (0.93) | ​ |  | (0.17) | ​
Diluted | ​ |  | 0.59 | ​ |  | (0.51) | ​ |  | 0.66 | ​ |  | (0.93) | ​ |  | (0.17) | ​
Weighted average common shares: | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Basic: | ​ |  | 50,277 | ​ |  | 50,140 | ​ |  | 50,181 | ​ |  | 50,181 | ​ |  | 50,195 | ​
Diluted: | ​ |  | 50,559 | ​ |  | 50,140 | ​ |  | 50,622 | ​ |  | 50,181 | ​ |  | 50,195 | ​
​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Year ended December 31, 2019 |
​ | ​ | First | ​ | Second | ​ | Third | ​ | Fourth | ​ | ​ | ​ |
​ | ​ | Quarter | ​ | Quarter | ​ | Quarter | ​ | Quarter | ​ | Year |
Operating revenues |  | $ | 723,694 |  | $ | 744,383 |  | $ | 760,295 |  | $ | 743,591 |  | $ | 2,971,963 | ​
Operating income | ​ |  | 96,419 | ​ |  | 144,093 | ​ |  | 146,441 | ​ |  | 125,305 | ​ | ​ | 512,258 | ​
Net income (1) | ​ |  | 88,181 | ​ |  | 88,052 | ​ |  | 91,339 | ​ |  | 72,527 | ​ | ​ | 340,099 | ​
Net income per common share: | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Basic | ​ |  | 1.71 | ​ |  | 1.72 | ​ |  | 1.80 | ​ |  | 1.44 | ​ | ​ | 6.68 | ​
Diluted | ​ |  | 1.69 | ​ |  | 1.71 | ​ |  | 1.79 | ​ |  | 1.43 | ​ | ​ | 6.62 | ​
Weighted average common shares: | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Basic: | ​ |  | 51,440 | ​ |  | 51,145 | ​ |  | 50,746 | ​ |  | 50,395 | ​ | ​ | 50,932 | ​
Diluted: | ​ |  | 52,098 | ​ |  | 51,477 | ​ |  | 51,129 | ​ |  | 50,796 | ​ | ​ | 51,375 | ​

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- Definition Tabular disclosure of quarterly financial data. Includes, but is not limited to, financial information for fiscal quarters, cumulative effect of a change in accounting principle and earnings per share data. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 270 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=121640914&loc=d3e1280-108306 + Details
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