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Dividends - Schedule of Dividends (Details) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2018
Mar. 31, 2018
Jun. 30, 2018
Jun. 30, 2017
Equity [Abstract]        
Cash dividend paid per common share (in dollars per share) $ 0.19250 $ 0.19125    
Total cash dividends paid $ 14,249 $ 14,149 $ 28,398 $ 27,374