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Quarterly Results of Operations | 12 Months Ended
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Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract] |
Quarterly Results of Operations | QUARTERLY RESULTS OF OPERATIONS (UNAUDITED)
(In thousands, except per share amounts) | First Quarter |  | Second Quarter |  | Third Quarter |  | Fourth Quarter
2017: |  |  |  |  |  |  |
Operating revenues | $ | 501,221 |  |  | $ | 519,508 |  |  | $ | 528,643 |  |  | $ | 567,365 |
Operating income | 25,972 |  |  | 36,913 |  |  | 35,874 |  |  | 45,061 |
Net income | 16,019 |  |  | 23,219 |  |  | 22,517 |  |  | 141,134 |
Basic earnings per share | 0.22 |  |  | 0.32 |  |  | 0.31 |  |  | 1.95 |
Diluted earnings per share | 0.22 |  |  | 0.32 |  |  | 0.31 |  |  | 1.94 |
(In thousands, except per share amounts) | First Quarter |  | Second Quarter |  | Third Quarter |  | Fourth Quarter
2016: |  |  |  |  |  |  |
Operating revenues | $ | 482,802 |  |  | $ | 498,681 |  |  | $ | 508,676 |  |  | $ | 518,832 |
Operating income | 32,487 |  |  | 29,553 |  |  | 29,074 |  |  | 34,956 |
Net income | 20,092 |  |  | 18,306 |  |  | 18,920 |  |  | 21,811 |
Basic earnings per share | 0.28 |  |  | 0.25 |  |  | 0.26 |  |  | 0.30 |
Diluted earnings per share | 0.28 |  |  | 0.25 |  |  | 0.26 |  |  | 0.30 |

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- Definition The entire disclosure for quarterly financial data. Includes, but is not limited to, tabular presentation of financial information for fiscal quarters, effect of year-end adjustments, and an explanation of matters or transactions that affect comparability of the information. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 270 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=68076893&loc=d3e1570-108306 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 270 -SubTopic 10 -Section 45 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=68064558&loc=d3e765-108305 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 270 -SubTopic 10 -Section 45 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=68064558&loc=d3e725-108305 + Details
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