Dividend Reinvestment Plan - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 25, 2020	Dec. 31, 2019	Jul. 11, 2017	Jul. 20, 2012
DIVIDEND REINVESTMENT PLAN
Common shares to be issued							2,000,000		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%
Maximum amount of optional additional shares available for purchase					$ 40
Estimated value per common share	$ 19.25				$ 19.25			$ 19.00
Purchase price per common share for dividend reinvestments	18.29				18.29			18.05
Purchase price per common share additional optional cash purchases	$ 19.25				$ 19.25			$ 19.00
Notice period to participants					10 days
Shares issued pursuant to dividend reinvestments					175,000	168,000
Shares issued pursuant to additional optional cash purchases under the plan					94,000	91,000
Value of shares issued pursuant to dividend reinvestments	$ 1,608	$ 1,584	$ 1,554	$ 1,479	$ 3,192	$ 3,033
Value of shares issued pursuant to additional optional cash purchases under the plan					$ 1,814	$ 1,724