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Earnings Per Share - Additional Information (Details) - shares
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Earnings Per Share [Abstract]        
Options and restricted common shares excluded from earnings per share calculation (in shares) 1,340,290 2,500,000 2,400,000.0 4,000,000.0