Stockholders' Equity (Details) - USD ($) $ / shares in Units, shares in Millions	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Aug. 31, 2021	Jul. 31, 2020
Subsidiary, Sale of Stock [Line Items]
Proceeds from issuance of common stock in at the market offering, net of issuance costs	$ 18,478,000	$ 62,446,000
Common stock
Subsidiary, Sale of Stock [Line Items]
Maximum aggregate offering price				$ 250,000,000
2020 Open Market Sales Agreement
Subsidiary, Sale of Stock [Line Items]
Issuance of common stock in at the market offering (in shares)		9.0
Proceeds from issuance of common stock in at the market offering, net of issuance costs		$ 63,800,000
Weighted-average sales price per share (in dollars per share)		$ 7.10
2020 Open Market Sales Agreement | Common stock
Subsidiary, Sale of Stock [Line Items]
Maximum aggregate offering price				$ 100,000,000
2021 Open Market Sales Agreement
Subsidiary, Sale of Stock [Line Items]
Issuance of common stock in at the market offering (in shares)	20.5
Proceeds from issuance of common stock in at the market offering, net of issuance costs	$ 18,900,000
Weighted-average sales price per share (in dollars per share)	$ 0.92
Commission on sale of stock per agreement (percent)	3.00%
2021 Open Market Sales Agreement | Common stock
Subsidiary, Sale of Stock [Line Items]
Maximum aggregate offering price			$ 150,000,000