Stockholders' Equity - Narrative (Details) $ / shares in Units, $ in Millions	1 Months Ended			12 Months Ended
	Mar. 31, 2020 USD ($) $ / shares shares	Aug. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($)	Dec. 31, 2020 USD ($) vote $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Jun. 30, 2020 USD ($)	May 21, 2019 shares	May 20, 2019 shares
Subsidiary, Sale of Stock [Line Items]
Preferred stock authorized (shares)				10,000,000	10,000,000.0
Preferred stock par value (in usd per share) | $ / shares				$ 0.001	$ 0.001
Preferred stock issued (shares)				0	0
Preferred stock outstanding (shares)				0	0
Common stock authorized (shares)				100,000,000	50,000,000		100,000,000.0	50,000,000.0
Common stock, par value (in usd per share) | $ / shares				$ 0.001	$ 0.001
Number of votes entitled to for each common share held | vote				1
Common stock issued (shares)				55,736,000	45,272,000
Common stock outstanding (shares)				55,736,000	45,272,000
Stock issued (shares)				200,000
Net proceeds from stock issuance | $				$ 4.9
Gross aggregate proceeds authorized under offering | $						$ 200.0
ATM
Subsidiary, Sale of Stock [Line Items]
Gross aggregate proceeds to be received upon stock issuance | $			$ 75.0
Stock issued (shares)				900,000	700,000
Net proceeds from stock issuance | $				$ 42.6	$ 30.3
Underwritten Public Offer
Subsidiary, Sale of Stock [Line Items]
Stock issued (shares)	9,800,000	6,000,000.0
Net proceeds from stock issuance | $	$ 221.7	$ 292.9
Stock offer price (in usd per share) | $ / shares	$ 23.50	$ 52.00
Over-Allotment option
Subsidiary, Sale of Stock [Line Items]
Stock issued (shares)	1,300,000