Stockholders' Equity (Restricted Stock) (Details) - Restricted stock units - 2014 Plan - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Stockholders' Equity, other disclosures
Requisite service period, annually	3 years
Granted	$ 7.06	$ 4.77	$ 8.02
Stock-based compensation expense	$ 9.3	$ 7.5	$ 11.2
Unrecognized compensation costs (in dollars)	$ 9.8
Weighted average period over which unrecognized compensation costs are expected to be recognized	2 years 10 days
Number of shares
Balance at beginning of the period	3,093,790	2,232,956
Granted	1,636,969	3,070,430
Vested	(1,452,893)	(1,150,707)
Forfeited	(478,314)	(1,058,889)
Balance at end of the period	2,799,552	3,093,790	2,232,956
Weighted average grant date fair value
Balance at beginning of the period	$ 6.97	$ 11.99
Granted	7.06	4.77	$ 8.02
Vested	6.42	10.06
Forfeited	2.31	7.82
Balance at end of the period	$ 8.11	$ 6.97	$ 11.99