Subsequent Events - Common Stock Continuous Offering Program (Details) - USD ($) $ / shares in Units, shares in Millions	1 Months Ended	3 Months Ended				9 Months Ended
	Nov. 04, 2020	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020
Subsequent Event [Line Items]
Issuance of Common Stock, net		$ 89,279,000	$ 886,926,000	$ 14,534,000	$ 27,544,000
Common Stock [Member]
Subsequent Event [Line Items]
Distribution agreement gross sales price (up to)		$ 750,000,000.0				$ 750,000,000.0
Common Stock Continuous Offering Program [Member] | Common Stock [Member]
Subsequent Event [Line Items]
Issuance of Common Stock, net (shares)						13.3
Issuance of Common Stock, net						$ 90,600,000
Proceeds from issuance of common stock						$ 89,400,000
Common Stock Continuous Offering Program [Member] | Common Stock [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Issuance of Common Stock, net (shares)	0.5
Issuance of Common Stock, net	$ 3,300,000
Proceeds from issuance of common stock	$ 3,200,000
Weighted Average [Member] | Common Stock Continuous Offering Program [Member] | Common Stock [Member]
Subsequent Event [Line Items]
Share price (in dollars per share)		$ 6.81				$ 6.81
Share price net of offering costs (in dollars per share)		$ 6.73				$ 6.73
Weighted Average [Member] | Common Stock Continuous Offering Program [Member] | Common Stock [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Share price (in dollars per share)	$ 7.04
Share price net of offering costs (in dollars per share)	$ 6.96