Stock-based Compensation - Additional Information (Narrative) (Details)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of common stock shares reserved for issuance under Long Term Incentive Plan     417,649
Number of common stock shares available for grant under Long Term Incentive Plan 7,808    
Weighted average period for unrecognized stock-based compensation expense 211 days    
Restricted Stock Award Units      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Granted (in shares) 35,752 45,914 389,057