Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Millions					1 Months Ended
	Dec. 09, 2019	Nov. 22, 2019	Jun. 25, 2018	May 25, 2018	Dec. 31, 2019	Dec. 31, 2018
Subsidiary, Sale of Stock [Line Items]
Common stock issued				14,375,000	88,817,741	62,516,627
Common stock, shares authorized					300,000,000	300,000,000
Common stock, par value					$ 0.0001	$ 0.0001
Public offering price	$ 6.25
Underwriting discounts and commissions					$ 8.9
Gross proceeds					143.8
Net proceeds					$ 134.9
Offering
Subsidiary, Sale of Stock [Line Items]
Common stock issued				12,500,000
Public offering price				$ 4.00
2019 offering
Subsidiary, Sale of Stock [Line Items]
Common stock issued	20,000,000
Underwriters' Option
Subsidiary, Sale of Stock [Line Items]
Common stock issued			1,875,000		3,000,000
Underwriting discounts and commissions			$ 3.7
Number of days to underwriters to sell additional common shares	30 days			30 days
Gross proceeds			57.5
Net proceeds			$ 53.8
Private Placement
Subsidiary, Sale of Stock [Line Items]
Common stock issued		2,873,563
Public offering price		$ 6.96
Net proceeds		$ 20.0
2019 Offering and Over-Allotment Option
Subsidiary, Sale of Stock [Line Items]
Common stock issued					23,000,000