XML 151 R134.htm IDEA: XBRL DOCUMENT v3.8.0.1
Net Income Per Share - Narrative (Details) - $ / shares
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2017
Earnings Per Share [Abstract]      
Stock options not included in the earnings per share calculation (in shares) 51,949 286,119  
Weighted average exercise price (in dollars per share) $ 19.26 $ 19.99 $ 16.71