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Equity Based Plans - Summary of Restricted Stock Granted to Directors, Officers and Employees Pursuant to Its Equity Plans (Details) - Restricted Stock [Member] - $ / shares
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Share-based Compensation [Abstract]      
Number of shares (in shares) 93,801 79,475 101,790
Weighted average fair value (in dollars per share) $ 78.63 $ 62.19 $ 51.59