Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity and Stock Based Compensation - Nonvested (Details)

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Stockholders' Equity and Stock Based Compensation - Nonvested (Details) - 2006 Plan and 2012 Plan - Restricted stock - USD ($)
$ / shares in Units, $ in Millions
3 Months Ended 12 Months Ended
Mar. 31, 2016
Mar. 31, 2015
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Shares          
Nonvested shares at the beginning of the period 123,329        
Granted (in shares) 160,350   44,000 98,689 56,500
Vested (in shares) (27,841)        
Forfeited (in shares)     (4,465) (34,487) (775)
Nonvested shares at the end of the period 255,838   123,329    
Weighted Average Grant Date Fair Value          
Nonvested shares at the beginning of period (in dollars per share) $ 16.34        
Granted (in dollars per share) 16.99        
Vested (in dollars per share) 14.33        
Nonvested shares at the end of period (in dollars per share) $ 15.22   $ 16.34    
Unrecognized compensation cost (in dollars) $ 3.9        
Weighted average period for recognition of unrecognized compensation cost 3 years 7 months 6 days        
Share-based compensation cost (in dollars) $ 0.4 $ 0.3