Common Stock and Preferred Stock (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended		3 Months Ended	9 Months Ended
	May 29, 2019	Jul. 31, 2019	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Common Stock and Preferred Stock
Convertible preferred stock converted into shares				15,109,950
Increase in common stock authorized (in shares)	90,000,000
Common stock, shares authorized	150,000,000				150,000,000		150,000,000
Preferred stock, shares authorized	10,000,000				10,000,000		10,000,000
Preferred stock, par value	$ 0.001				$ 0.001		$ 0.001
Preferred stock, shares issued					0		0
Preferred stock, shares outstanding					0		0
Sale of common shares (in shares)		450,000	3,000,000
Purchase price (in dollars per share)		$ 15.00	$ 15.00
Proceeds from sale of common stock					$ 48,348	$ 77,839