Annual report pursuant to Section 13 and 15(d)

Supplemental Information on Oil and Natural Gas Properties (unaudited) (Standardized Measure of Discounted Future Cash Flows Relating to Proved Reserves Disclosure) (Details)

v3.3.1.900
Supplemental Information on Oil and Natural Gas Properties (unaudited) (Standardized Measure of Discounted Future Cash Flows Relating to Proved Reserves Disclosure) (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves, Future Net Cash Flows [Abstract]            
Future cash inflows       $ 2,227,463 $ 2,492,178 $ 1,193,299
Production       (827,555) (873,469) (357,005)
Development and net abandonment       (239,100) (288,081) (155,667)
Future net inflows before income taxes       1,160,808 1,330,628 680,627
Future income taxes         (164,490) (68,239)
Future net cash flows       1,160,808 1,166,138 612,388
10% discount factor       (589,918) (586,596) (328,442)
Standardized measure of discounted future net cash flows $ 579,542 $ 283,946 $ 231,148 $ 570,890 $ 579,542 $ 283,946
Increase (Decrease) in Standardized Measure of Discounted Future Net Cash Flow Relating to Proved Oil and Gas Reserves [Roll Forward]            
Standardized measure at the beginning of the period 579,542 283,946 231,148      
Sales and transfers, net of production costs (110,476) (120,518) (78,661)      
Net change in sales and transfer prices, net of production costs (286,660) (156,066) (46,088)      
Net change due to purchases and sales of in place reserves 37,616 111,331 (145,711)      
Extensions, discoveries, and improved recovery, net of future production and development costs incurred 184,469 299,192 212,431      
Changes in future development cost 108,216 186,605 153,983      
Revisions of quantity estimates (12,625) (7,673) (68,958)      
Accretion of discount 62,968 30,114 25,010      
Net change in income taxes 35,407 (32,940) 1,751      
Changes in production rates, timing and other (27,567) (14,449) (959)      
Aggregate change (8,652) 295,596 52,798      
Standardized measure at the end of the period $ 570,890 $ 579,542 $ 283,946