Annual report pursuant to Section 13 and 15(d)

Supplemental Information on Oil and Natural Gas Properties (unaudited) (Capitalized Costs Relating to Oil and Natural Gas Activities) (Details)

v3.6.0.2
Supplemental Information on Oil and Natural Gas Properties (unaudited) (Capitalized Costs Relating to Oil and Natural Gas Activities) (Details) - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2015
Sep. 30, 2015
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Evaluated Properties              
Beginning of period balance   $ 2,335,223     $ 2,335,223 $ 2,077,985 $ 1,701,577
Capitalized G&A expenses         12,222 10,529 10,071
Property acquisition costs         216,561 26,726 94,541
Exploration costs         38,612 81,320 118,251
Development costs         151,735 138,663 153,545
End of period balance     $ 2,335,223   2,754,353 2,335,223 2,077,985
Unevaluated Properties              
Beginning of period balance   132,181     132,181 142,525 43,222
Property acquisition costs         548,673 5,520 128,342
Exploration costs         8,631 4,576 11,177
Capitalized interest expenses         19,857 10,459 4,295
Transfers to Evaluated Properties         (40,621) (30,899) (44,511)
End of period balance     132,181   668,721 132,181 142,525
Accumulated depreciation, depletion and amortization:              
Beginning of period balance   1,756,018     1,756,018 1,478,355 1,420,612
Provision charged to expense         71,330 69,228 56,663
Write-down of oil and natural gas properties $ 61,012 $ 34,776 121,134 $ 87,301 95,788 208,435  
Sale of mineral interests         24,537   1,080
End of period balance     $ 1,756,018   $ 1,947,673 $ 1,756,018 $ 1,478,355