Share Based Awards - Options by price (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Number of shares outstanding	2,898,977
Weighted average remaining contractual term, outstanding	4 years 10 months 21 days
Weighted average exercise price, outstanding	$ 5.17
Number of shares exercisable	2,410,434
Weighted average exercise price, exercisable	$ 5.32
Vested options exercised, intrinsic value	$ 3.0	$ 5.7	$ 2.3
Options granted, grant date fair value per share	$ 2.28	$ 2.43	$ 1.74
$0.55 - $3.85
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Exercise price, lower limit	0.55
Exercise price, upper limit	$ 3.85
Number of shares outstanding	753,487
Weighted average remaining contractual term, outstanding	3 years 10 months 6 days
Weighted average exercise price, outstanding	$ 3.18
Number of shares exercisable	646,194
Weighted average exercise price, exercisable	$ 3.09
$4.06 - $4.66
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Exercise price, lower limit	4.06
Exercise price, upper limit	$ 4.66
Number of shares outstanding	650,522
Weighted average remaining contractual term, outstanding	5 years 6 months 29 days
Weighted average exercise price, outstanding	$ 4.48
Number of shares exercisable	450,522
Weighted average exercise price, exercisable	$ 4.44
$4.70 - $5.77
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Exercise price, lower limit	4.70
Exercise price, upper limit	$ 5.77
Number of shares outstanding	694,723
Weighted average remaining contractual term, outstanding	5 years 6 months 15 days
Weighted average exercise price, outstanding	$ 5.32
Number of shares exercisable	513,473
Weighted average exercise price, exercisable	$ 5.53
$6.20 - $8.39
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Exercise price, lower limit	6.20
Exercise price, upper limit	$ 8.39
Number of shares outstanding	590,810
Weighted average remaining contractual term, outstanding	4 years 9 months 29 days
Weighted average exercise price, outstanding	$ 6.76
Number of shares exercisable	590,810
Weighted average exercise price, exercisable	$ 6.76
$8.80 - $12.05
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Exercise price, lower limit	8.80
Exercise price, upper limit	$ 12.05
Number of shares outstanding	209,435
Weighted average remaining contractual term, outstanding	4 years 4 months 21 days
Weighted average exercise price, outstanding	$ 9.54
Number of shares exercisable	209,435
Weighted average exercise price, exercisable	$ 9.54