Stockholders' Equity, Stock Plans and Stock-based Compensation Expense - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Shares Available For Grant
Balance (in shares)	1,085,170	761,705	1,141,305
Additional shares reserved (in shares)	450,000	600,000	700,000
Options granted (in shares)	(172,139)	(71,088)
Options cancelled (expired or forfeited) (in shares)	30,173	76,553	51,208
Stock awards granted (in shares)	(744,949)	(804,949)	(1,538,128)
Stock awards canceled (expired or forfeited) (in shares)	299,092	522,949	407,320
Balance (in shares)	947,347	1,085,170	761,705	1,141,305
Number of Shares
Balance (in shares)	217,007	295,699	507,705
Options exercised (in shares)	(71,798)	(73,227)	(160,798)
Options granted (in shares)	172,139	71,088
Options cancelled (expired or forfeited) (in shares)	(30,173)	(76,553)	(51,208)
Balance (in shares)	287,175	217,007	295,699	507,705
Exercisable (in shares)	83,855
Vested and expected to vest (in shares)	287,175
Weighted- Average Exercise Price
Balance (in dollars per share)	$ 22.35	$ 25.52	$ 20.52
Options granted (in dollars per share)	30.71	14.85
Options exercised (in dollars per share)	22.02	12.91	10.03
Options cancelled (expired or forfeited) (in dollars per share)	37.14	36.65	24.61
Balance (in dollars per share)	25.89	$ 22.35	$ 25.52	$ 20.52
Exercisable (in dollars per share)	24.14
Vested and expected to vest (in dollars per share)	$ 25.89
Weighted-Average Remaining Contractual Life
Balance	4 years 11 months 1 day	3 years 9 months	3 years 2 months 8 days	3 years 6 months 7 days
Exercisable	2 years 10 months 9 days
Vested and expected to vest	4 years 11 months 1 day
Aggregate Intrinsic Value
Balance	$ 4,460	$ 1,470	$ 3,040	$ 2,000
Exercisable	1,470
Vested and expected to vest	$ 4,460