Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity (Summary of Nonvested Restricted Stock Award Activity) (Details)

v3.8.0.1
Stockholders' Equity (Summary of Nonvested Restricted Stock Award Activity) (Details) - Stock Option Plan - Restricted Stock - $ / shares
shares in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Shares      
Nonvested at beginning of period (in shares) 1,465    
Granted (in shares) 607    
Vested (in shares) (894)    
Forfeited (in shares) (5)    
Nonvested at end of period (in shares) 1,173 1,465  
Weighted Average Grant Date Fair Value      
Nonvested at beginning of period (USD per share) $ 14.41    
Granted (USD per share) 23.24 $ 17.87 $ 15.06
Vested (USD per share) 16.22    
Forfeited (USD per share) 18.48    
Nonvested at end of period (USD per share) $ 17.58 $ 14.41