Dividend Reinvestment Plan - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Jul. 11, 2017	Jul. 20, 2012
DIVIDEND REINVESTMENT PLAN
Common shares to be issued				2,000,000	2,000,000
Minimum percentage of cash dividends	25.00%
Maximum additional cash purchase of common shares per fiscal quarter	$ 10
Percentage estimated value for dividend reinvestments	95.00%
Percentage estimated value for additional optional cash purchases	100.00%
Estimated value per common share	$ 18.50		$ 16.50
Maximum value of common shares that my be purchased or received via transfer by participants under the dividend reivestment plan	$ 40
Purchase price per common share for dividend reinvestments	$ 17.58		15.680
Purchase price per common share additional optional cash purchases	$ 18.50		$ 16.50
Notice period to participants	10 days
Shares issued pursuant to dividend reinvestments	79,000	82,000
Shares were issued pursuant to additional optional cash purchases under the plan	76,000	44,000