Preferred Stock and Common Stock Warrants - Assumptions (Details) - Common Stock Warrants	Jun. 30, 2019 Y $ / shares	Dec. 31, 2018 Y $ / shares
Warrants
Stock price	$ 6.32	$ 5.40
Measurement Input, Exercise Price
Warrants
Warrants and Rights Outstanding, Measurement Input	0.01	0.01
Measurement Input, Risk Free Interest Rate
Warrants
Warrants and Rights Outstanding, Measurement Input	1.8	2.5
Measurement Input, Price Volatility
Warrants
Warrants and Rights Outstanding, Measurement Input	27.6	33.1
Measurement Input, Expected Term
Warrants
Warrants and Rights Outstanding, Measurement Input | Y	2.4	2.7