Mezzanine and Stockholders' Equity - Summary of Warrant (Details) - USD ($) $ / shares in Units, $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Shares
Warrants outstanding, beginning balance (in shares)	3,331,995
Warrants granted (in shares)	0
Warrants exercised (in shares)	(133,221)
Warrants expired/forfeited (in shares)	0
Warrants outstanding, ending balance (in shares)	3,198,774	3,331,995
Weighted Average Exercise Price
Warrants outstanding, beginning balance (in dollars per share)	$ 9.93
Warrants granted (in dollars per share)	0.00
Warrants exercised (in dollars per share)	9.21
Warrants expired/forfeited (in dollars per share)	0.00
Warrants outstanding, ending balance (in dollars per share)	$ 9.96	$ 9.93
Weighted Average Remaining Contractual Term
Warrants outstanding	2 years 3 months 4 days	2 years 11 months 19 days
Aggregate Intrinsic Value
Warrants outstanding, beginning balance	$ 33.1
Warrants granted	0.0
Warrants exercised	1.4
Warrants expired/forfeited	0.0
Warrants outstanding, ending balance	$ 24.5	$ 33.1