Annual report pursuant to Section 13 and 15(d)

Earnings Per Share - Schedule of Calculation of Basic and Diluted Earnings Per Common Share (Details)

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Earnings Per Share - Schedule of Calculation of Basic and Diluted Earnings Per Common Share (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
3 Months Ended 12 Months Ended
Dec. 31, 2015
[1]
Sep. 30, 2015
[1]
Jun. 30, 2015
[1]
Mar. 31, 2015
[1]
Dec. 31, 2014
Sep. 30, 2014
Jun. 30, 2014
Mar. 31, 2014
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Earnings Per Share, Basic and Diluted [Abstract]                      
Net income (loss) $ (51,606) $ (477,568) $ (260,449) $ (255,095) $ (33,371) $ 684 $ 9,837 $ 11,189 $ (1,044,718) $ (11,661) $ 51,322
Less portion allocated to nonvested shares                   269 303
Net income (loss) allocated to common shares                 $ (1,044,718) $ (11,930) $ 51,019
Weighted average common shares outstanding                 75,931 75,609 75,239
Basic and diluted earnings (loss) per common share $ (0.68) [2] $ (6.29) [2] $ (3.43) [2] $ (3.36) [2] $ (0.44) [2] $ 0.01 [2] $ 0.13 [2] $ 0.15 [2] $ (13.76) $ (0.16) $ 0.68
Shares excluded due to being anti-dilutive (weighted-average)                 2,195 2,097  
[1] During 2015, we recorded in first, second, third and fourth quarter ceiling test write-downs of oil and natural gas properties of $260.4 million, $252.8 million, $441.6 million and $32.4 million, respectively. See Note 1 for additional information.
[2] The sum of the individual quarterly earnings (loss) per share may not agree with the year loss per share because each quarterly calculation is based on the income for that quarter and the weighted average number of shares outstanding during that quarter.