Annual report pursuant to Section 13 and 15(d)

Share-Based Compensation (Narrative) (Details)

v3.8.0.1
Share-Based Compensation (Narrative) (Details) - USD ($)
$ / shares in Units, $ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Payments to settle vested liability share-based awards $ 13,173 $ 10,300 $ 3,925
Cash-settleable restricted stock unit awards 4,621 $ 8,919  
Vesting in 2018      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Cash-settleable restricted stock unit awards $ 3,062    
Unvested RSUs      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Weighted average period over which expense is expected to be recognized 2 years    
Stock options      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of years company issued no stock options 3 years    
Vested, shares 0    
Forfeited, shares 0    
Exercised, shares 0    
Expired, shares 15,000    
Outstanding, shares 0 15,000 15,000
Exercisable, shares 15,000 15,000 30,000
Share-based payment award outstanding aggregate intrinsic value $ 0 $ 0 $ 0
Outstanding, end of year, weighted average exercise price per option   $ 14.37 $ 14.37
Outstanding options weighted-average remaining contract life per unit   3 months 18 days 1 year 3 months 18 days
RSU equity awards      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Weighted average period over which expense is expected to be recognized 1 year 11 months 9 days    
Granted 1,173,000 684,090 559,556
Granted, grant date fair value per share $ 12.25 $ 12.63 $ 8.98
Fair value of shares vested   $ 2,608 $ 5,425
Vested in period 797,000    
Market-based Cashsettleable R S U Awards      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vested in period 335,471 281,792  
Market-based Cashsettleable R S U Awards | Vesting Maximum      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based compensation arrangement vesting rights, percentage 200.00% 200.00%  
Market-based Cashsettleable R S U Awards | Vested at between 142% to 200%      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Payments to settle vested liability share-based awards $ 3,986    
Market-based Cashsettleable R S U Awards | Vested at 200%      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Payments to settle vested liability share-based awards 8,662    
Market-based RSUs      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Fair value of shares vested $ 9,045    
Vested in period 73,000    
Share-based compensation arrangement vesting rights, percentage 142.00%    
Cash-settleable RSU awards      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Weighted average period over which expense is expected to be recognized 2 years    
Cash-settleable RSU awards | Vesting Maximum      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based compensation arrangement vesting rights, percentage 200.00%    
Non-Market Based Cash-settleable RSU Awards      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vested in period 43,031 45,282  
Payments to settle vested liability share-based awards $ 526 $ 493  
Non-Market Based Cash-settleable RSU Awards | Vesting Maximum      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based compensation arrangement vesting rights, percentage 200.00%    
2011 Plan      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of shares available for grant 1,338,356