Annual report pursuant to Section 13 and 15(d)

Summary of Unaudited Quarterly Financial Information - Summary (Details)

v3.10.0.1
Summary of Unaudited Quarterly Financial Information - Summary (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
3 Months Ended 12 Months Ended
Dec. 31, 2018
Sep. 30, 2018
Jun. 30, 2018
Mar. 31, 2018
Dec. 31, 2017
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]                      
Total revenues $ 50,465 $ 33,375 $ 27,995 $ 29,267 $ 59,590 $ 45,663 $ 90,043 $ 56,157 $ 251,453 $ 141,102 $ 108,973
Total operating costs and expenses 22,113 16,882 14,980 19,051 26,441 22,301 19,868 19,116 87,726 73,026 65,088
Income tax (expense) benefit (37,674) (3,645) (2,242) (1,114) 14,307 (11,864) (22,419) (10,033) (30,009) (44,675) (10,327)
Net Income (loss) $ (7,007) $ 8,426 $ 6,058 $ 5,079 $ (42,482) $ 67,362 $ 73,160 $ 45,279 $ 143,321 $ 12,556 $ (1,636)
Basic per share amounts:                      
Net income (loss) - Basic (USD per share) $ (0.33) $ 0.40 $ 0.29 $ 0.24 $ (2.02) $ 3.19 $ 3.45 $ 2.13 $ 6.77 [1] $ 0.60 [1] $ (0.08) [1]
Diluted per share amounts:                      
Net income (loss) - Diluted (USD per share) $ (0.33) $ 0.36 $ 0.26 $ 0.22 $ (2.02) $ 2.80 $ 2.99 $ 1.83 $ 5.96 [1] $ 0.53 [1] $ (0.08) [1]
Weighted average shares—basic (shares) 21,109 21,071 21,013 20,938 21,071 21,148 21,212 21,209 21,160 21,032 20,831
Weighted average shares—diluted (shares) 21,109 23,551 23,216 23,019 21,071 24,052 24,438 24,800 24,067 23,481 20,831
[1] The sum of net income per share amounts may not equal the total due to rounding