Common Stock-Antidilutive Securities (Details) - shares
shares in Thousands
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]      
Antidilutive securities excluded from computation of earnings per share (in shares) 494    
Stock options      
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]      
Antidilutive securities excluded from computation of earnings per share (in shares) 24 0 1,212
Stock compensation plan      
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]      
Antidilutive securities excluded from computation of earnings per share (in shares) [1] 1,045 1,568 1,290
[1] (1) Compensation cost is recognized for these performance stock grants based on expected achievement rates; however no consideration is given for these performance stock grants when calculating earnings per share until the performance measurements have actually been achieved. As of December 31, 2015, these performance measurements had not been achieved.