Annual report pursuant to Section 13 and 15(d)

Share-Based Compensation (Share-Based Compensation Expense) (Details)

v3.3.1.900
Share-Based Compensation (Share-Based Compensation Expense) (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based compensation expense - Equity-based $ 4,063 $ 4,493 $ 4,194
Share-based compensation expense - Liability-based 11,437 6,918 5,347
Share-based compensation - capitalized oil and gas properties 6,201 4,176 3,791
RSU RSU equity awards [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based compensation expense - Equity-based 3,797 4,223 3,975
Cash-settleable RSU awards [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based compensation expense - Liability-based 11,437 6,918 5,347
401(k) contributions in shares [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based compensation expense - Equity-based 266 270 219
General and Administrative Expense [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
share-based compensation $ 9,299 $ 7,235 $ 5,751