Issuances of Common Stock - Dividend Reinvestment and Stock Purchase Plan (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Dividend Reinvestment and Stock Purchase Plan
Gross proceeds			$ 4,815	$ 4,098
DRSPP
Dividend Reinvestment and Stock Purchase Plan
Dividend Reinvestment and Stock Purchase Plan, authorized shares (in shares)	26,000,000		26,000,000
Shares remaining for future issuance (in shares)	11,573,851		11,573,851
Common stock | DRSPP
Dividend Reinvestment and Stock Purchase Plan
Shares of common stock issued (in shares)	44,817	27,520	78,817	59,418
Gross proceeds	$ 2,400	$ 1,900	$ 4,800	$ 4,100