Capital Stock - Convertible Preferred Stock Warrant (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Class of Warrant or Right [Line Items]
Warrants to purchase (in shares)	49,997
Reclassification of redeemable convertible preferred stock warrant liability to additional paid-in capital	$ 503
Preferred stock warrant liability		$ 380
Preferred Stock Warrants
Class of Warrant or Right [Line Items]
Warrants to purchase (in shares)	49,997
Reclassification of redeemable convertible preferred stock warrant liability to additional paid-in capital	$ 500
Preferred stock warrant liability	$ 0	$ 400