Annual report pursuant to Section 13 and 15(d)

Share-Based Compensation (Schedule of Unvested Restricted Stock Units Activity) (Details)

v3.8.0.1
Share-Based Compensation (Schedule of Unvested Restricted Stock Units Activity) (Details) - USD ($)
$ / shares in Units, $ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
RSU equity awards      
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]      
Outstanding at the beginning of the period 1,448,000    
Granted 1,173,000 684,090 559,556
Vested (797,000)    
Forfeited (34,000)    
Outstanding at the end of the period 1,790,000 1,448,000  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]      
Outstanding at the beginning of the period, Grant Date Fair Value per Share $ 10.81    
Granted, grant date fair value per share 12.25 $ 12.63 $ 8.98
Vested, grant date fair value per share 11.35    
Forfeited, grant date fair value per share 9.57    
Outstanding at the end of the period, grant date fair value per share $ 11.54 $ 10.81  
Weighted average period over which expense is expected to be recognized 1 year 11 months 9 days    
Fair value of shares vested   $ 2,608 $ 5,425
Market-based Cashsettleable R S U Awards      
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]      
Vested (335,471) (281,792)  
Market-based Cashsettleable R S U Awards | Vesting range 0 to 200%      
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]      
Outstanding at the end of the period 89,000    
Market-based Cashsettleable R S U Awards | Vesting Minimum      
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]      
Share-based compensation arrangement vesting rights, percentage 0.00%    
Market-based Cashsettleable R S U Awards | Vesting Maximum      
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]      
Share-based compensation arrangement vesting rights, percentage 200.00% 200.00%  
Market-based RSUs      
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]      
Vested (73,000)    
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]      
Share-based compensation arrangement vesting rights, percentage 142.00%    
Fair value of shares vested $ 9,045