Mezzanine and Stockholders' Equity - Summary of Warrant (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Shares
Warrants outstanding (in shares)	3,154,590	3,331,995	3,648,541
Warrants granted (in shares)	0	0
Warrants exercised (in shares)	(1,247,644)	(177,405)	(286,357)
Warrants forfeited (in shares)	(28,820)	0	(30,189)
Warrants outstanding (in shares)	1,878,126	3,154,590	3,331,995	3,648,541
Weighted Average Exercise Price
Warrants outstanding (in dollars per share)	$ 9.96	$ 9.93	$ 9.75
Warrants granted (in dollars per share)	0	0
Warrants exercised (in dollars per share)	9.33	9.32	7.84
Warrants forfeited (in dollars per share)	9.00		4.50
Warrants outstanding (in dollars per share)	$ 10.39	$ 9.96	$ 9.93	$ 9.75
Weighted Average Remaining Contractual Term (Years)
Warrants outstanding balance	1 year 7 months 17 days	2 years 3 days	2 years 11 months 19 days	3 years 8 months 26 days
Aggregate Intrinsic Value (in millions)
Warrants outstanding, beginning balance	$ 26.7	$ 33.1	$ 52.0
Warrants granted	0.0	0.0
Warrants exercised	9.8	1.6	3.0
Warrants forfeited	0.0	0.0	0.0
Warrants outstanding, ending balance	$ 14.8	$ 26.7	$ 33.1	$ 52.0