Common Stock - Narrative (Details)	3 Months Ended			9 Months Ended
	Sep. 30, 2020 shares	Jun. 30, 2020 Agreement	Sep. 30, 2019 shares	Sep. 30, 2020 shares	Sep. 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	821,196		597,672	1,557,465	1,020,633
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	1,800,000			1,800,000
Sales Agency Agreement | Common Stock [Member]
Class Of Stock [Line Items]
Shares issued under sales agency agreements	800,000			1,400,000