Preferred Stock and Common Stock - At-the-market equity offering program (Details) - Private Placement - USD ($)	1 Months Ended	3 Months Ended
	Jul. 31, 2019	Mar. 31, 2019
Class of Stock [Line Items]
Proceeds from sale of stock		$ 0
Common Stock
Class of Stock [Line Items]
Number of shares sold (in shares)		0
Cantor Fitzgerald & Co.
Class of Stock [Line Items]
Sale of stock, issuance costs percentage	3.00%
Cantor Fitzgerald & Co. | Common Stock
Class of Stock [Line Items]
Sale of stock, authorized amount (in shares)	$ 50,000,000