Employee Benefit Plans and Stock-Based Compensation - Options (Details) - Options - USD ($) $ / shares in Units, shares in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of Options Outstanding [Roll Forward]
Options outstanding, beginning of period (in shares)	2,654	2,666	3,294
Granted (in shares)	430	246	184
Exercised (in shares)	(113)	(238)	(762)
Canceled and expired (in shares)	(18)	(20)	(50)
Options outstanding, end of period (in shares)	2,953	2,654	2,666	3,294
Options vested and unvested options expected to vest, net of forfeitures, end of period (in shares)	2,914
Options exercisable, end of period (in shares)	2,169
Weighted-average Exercise Price [Roll Forward]
Options outstanding, beginning of period (in dollars per share)	$ 4.09	$ 3.81	$ 3.38
Granted (in dollars per share)	3.06	5.77	8.99
Exercised (in dollars per share)	2.37	2.64	3.25
Canceled and expired (in dollars per share)	4.47	4.40	3.47
Options outstanding, end of period (in dollars per share)	4.00	4.09	3.81	$ 3.38
Options vested and unvested options expected to vest, net of forfeitures (in dollars per share)	4.00
Options exercisable, end of period (in dollars per share)	3.81
Weighted-average grant date fair value of stock options granted (in dollars per share)	$ 1.48	$ 2.74	$ 3.67
Weighted average Remaining Contractual Life [Abstract]
Options outstanding	5 years 11 months 12 days	6 years 3 months 11 days	6 years 10 months 13 days	7 years 2 months 23 days
Options vested and unvested options expected to vest, net of forfeitures, end of period	5 years 10 months 24 days
Option exercisable, end of period	4 years 9 months 29 days
Aggregate Intrinsic Value [Abstract]
Options outstanding, beginning of period	$ 2,720,000	$ 13,149,000	$ 5,301,000
Exercised	266,000	666,000	4,030,000
Options outstanding, end of period	3,040,000	$ 2,720,000	$ 13,149,000	$ 5,301,000
Options vested and expected to vest, end of period	3,001,000
Options exercisable, end of period	$ 2,484,000