Annual report pursuant to Section 13 and 15(d)

Share-Based Awards and Cash-Based Awards - Summary of Compensation Expense Related to Share-Based Awards and Cash-Based Awards (Details)

v3.8.0.1
Share-Based Awards and Cash-Based Awards - Summary of Compensation Expense Related to Share-Based Awards and Cash-Based Awards (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]      
Share-based compensation charged to operating income $ 8,065 $ 11,013 $ 10,242
Total charged to operating income 15,198 11,013 10,373
General And Administrative Expense      
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]      
Share-based compensation charged to operating income 8,065 $ 11,013 10,242
Cash-based incentive compensation charged to operating income [1] 5,032   (233)
Lease Operating Expense      
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]      
Cash-based incentive compensation charged to operating income $ 2,101   $ 364
[1] Adjustments to true up estimates to actual payments resulted in net credit balances to expense in 2015.