Common Stock - Narrative (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2020 Agreement shares	Jun. 30, 2019 shares	Jun. 30, 2020 shares	Jun. 30, 2019 shares	Dec. 31, 2019 shares
Class Of Stock [Line Items]
Common stock, shares authorized	200,000,000		200,000,000		200,000,000
Common Stock [Member]
Class Of Stock [Line Items]
Shares issued under sales agency agreements	621,032	361,385	736,269	422,961
Sales Agency Agreement
Class Of Stock [Line Items]
Number of agreement | Agreement	4
Common stock, shares authorized	3,200,000		3,200,000
Common stock shares authorized under sales agency agreements remaining shares authorized to sell	2,600,000		2,600,000
Sales Agency Agreement | Common Stock [Member]
Class Of Stock [Line Items]
Shares issued under sales agency agreements	0.6		0.6
Expired Sales Agency Agreements
Class Of Stock [Line Items]
Shares issued under sales agency agreements			0
Agreement expiration date			Feb. 29, 2020