Stock-Based Compensation Schedule of Share-based Compensation Rollforward (Details) - 2007 Stock Incentive Plan - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Shares
Options outstanding, beginning of year (in shares)	1,060	1,442	1,288
Number of options granted	658	39	758
Options exercised (in shares)	(295)	(40)	0
Options canceled (in shares)	(158)	(381)	(604)
Weighted-average remaining contractual term for options outstanding (In years)	2 years 10 months 24 days
Options outstanding, end of year (in shares)	1,265	1,060	1,442
Weighted-average remaining contractual term for options outstanding (In years)	2 years 10 months 24 days
Options vested and expected to vest (in shares)	1,265
Options subject to exercise (in shares)	394	540	572
Weighted Average Exercise Price
Options outstanding, weighted-average exercise price, beginning of year (dollars per share)	$ 2.93	$ 3.51	$ 6.18
Options granted, weighted-average exercise price (dollars per share)	4.90	3.11	2.24
Options exercised, weighted-average exercise price (dollars per share)	2.63	2.55	0
Options canceled, weighted-average exercise price (dollars per share)	4.31	5.20	7.60
Options outstanding, weighted-average exercise price, end of year (dollars per share)	3.85	2.93	3.51
Weighted-average exercise price for options subject to exercise (dollars per share)	$ 2.96	$ 3.51	$ 5.29
Share-based Payment Arrangement, Option, Exercise Price Range, Exercisable, Weighted Average Remaining Contractual Term	3 years 6 months
Aggregate intrinsic value of options outstanding (value)	$ 5,317
Weighted-average exercise price for options vested and expected to vest (dollars per share)	$ 3.85
Aggregate intrinsic value for options subject to exercise (value)	$ 2,069
Aggregate intrinsic value of options vested and expected to vest (value)	$ 5,317