Dividends - Schedule of Dividends (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2017	Sep. 30, 2016
Equity [Abstract]
Cash dividends paid per common share (in dollars per share)	$ 0.18875	$ 0.18750	$ 0.18625
Total cash dividends paid	$ 13,883	$ 13,750	$ 13,624	$ 41,302	$ 39,849