Annual report pursuant to Section 13 and 15(d)

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

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Earnings/ (Loss) Per Share - Schedule of Calculation of Basic and Diluted Earnings (Loss) Per Common Share (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
 3 Months Ended 12 Months Ended
Dec. 31, 2017
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2016
 [1]
Sep. 30, 2016
 [1]
Jun. 30, 2016
 [1]
Mar. 31, 2016
 [1]
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Earnings Per Share, Basic and Diluted [Abstract]                      
Net income (loss) $ 23,365 $ (1,297) $ 33,315 $ 24,299 $ 16,483 $ 45,928 $ (120,922) $ (190,509) $ 79,682 $ (249,020) $ (1,044,718)
Less portion allocated to nonvested shares                 3,244    
Net income (loss) allocated to common shares                 $ 76,438 $ (249,020) $ (1,044,718)
Weighted average common shares outstanding                 137,617 95,644 75,931
Basic and diluted earnings (loss) per common share $ 0.16 $ (0.01) $ 0.23 $ 0.17 $ 0.12 [2] $ 0.48 [2] $ (1.58) [2] $ (2.49) [2] $ 0.56 $ (2.60) $ (13.76)
Shares excluded due to being anti-dilutive (weighted-average)                   5,269 2,195
[1] During 2016, we recorded in first, second and third quarter ceiling test write-downs of oil and natural gas properties of $116.6 million, $104.6 million and $57.9 million, respectively. In the third quarter of 2016, we recorded a gain on exchange of debt of $123.9 million. See Note 1 and Note 2 for additional information.
[2] The sum of the individual quarterly earnings (loss) per share does 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. During the third quarter of 2016, 60.4 million shares of common stock were issued in conjunction with the Exchange Transaction.