Quarterly Financial Data - Summary of Condensed Quarterly Results of Operations (Detail) - USD ($) $ / shares in Units, $ in Thousands |
3 Months Ended | 12 Months Ended | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Dec. 31, 2015 |
Sep. 30, 2015 |
Jun. 30, 2015 |
Mar. 31, 2015 |
Dec. 31, 2014 |
Sep. 30, 2014 |
Jun. 30, 2014 |
Mar. 31, 2014 |
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
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| Quarterly Financial Information Disclosure [Abstract] | |||||||||||
| Operating revenues | $ 186,751 | $ 214,733 | $ 198,547 | $ 204,197 | $ 210,760 | $ 216,294 | $ 212,145 | $ 197,071 | $ 804,228 | $ 836,270 | $ 856,500 |
| Gain (loss) on disposition of assets, net | (577) | 165 | 66 | 7 | 523 | (56) | (242) | (1,073) | (339) | (848) | 16,604 |
| Earnings (loss) before income taxes | 938 | 14,290 | 11,044 | 16,984 | 11,651 | 28,277 | 21,700 | (8,513) | 43,256 | 53,115 | 90,141 |
| Net earnings (loss) | $ 2,438 | $ 7,669 | $ 6,454 | $ 10,363 | $ 7,392 | $ 17,249 | $ 13,368 | $ (5,321) | $ 26,924 | $ 32,688 | $ 58,956 |
| Net earnings (loss) per share | |||||||||||
| Basic | $ 0.16 | $ 0.49 | $ 0.41 | $ 0.67 | $ 0.48 | $ 1.11 | $ 0.86 | $ (0.34) | |||
| Diluted | $ 0.16 | $ 0.49 | $ 0.41 | $ 0.66 | $ 0.47 | $ 1.10 | $ 0.85 | $ (0.34) | |||
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- References No definition available.
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- Definition Amount of gain (loss) on sale or disposal of property, plant and equipment assets, excluding oil and gas property and timber property. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition This element represents the income or loss from continuing operations attributable to the economic entity which may also be defined as revenue less expenses from ongoing operations, after income or loss from equity method investments, but before income taxes, extraordinary items, and noncontrolling interest. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition The amount of net income (loss) from extraordinary items, net of related tax effect, per each share of common stock or unit outstanding during the reporting period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition The amount of net income (loss) for the period attributable to extraordinary items that is available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition The portion of profit or loss for the period, net of income taxes, which is attributable to the parent. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- References No definition available.
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- Definition Aggregate revenue during the period from services rendered in the normal course of business, after deducting allowances and discounts. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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