Summary Of Significant Accounting Policies (Numerators And Denominators In The Calculation Of Basic And Diluted Net Loss Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	12 Months Ended
Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Numerator:
Net loss	$ (2,522)	$ (3,518)	$ (3,015)	$ (5,795)	$ (4,517)	$ (3,671)	$ (3,374)	$ (2,583)	$ (2,156)	$ (3,534)	$ (3,246)	$ (3,450)	$ (14,850)	$ (14,145)	$ (12,386)
Denominator:
Shares used in computing net loss per share, basic and diluted													45,638	45,356	45,269
Net loss per share, basic and diluted	$ (0.06)	$ (0.08)	$ (0.07)	$ (0.13)	$ (0.10)	$ (0.08)	$ (0.07)	$ (0.06)	$ (0.05)	$ (0.08)	$ (0.07)	$ (0.08)	$ (0.33)	$ (0.31)	$ (0.27)
Dilutive common shares excluded from net loss per share, diluted													17,745	17,421	10,625

Summary Of Significant Accounting Policies (Numerators And Denominators In The Calculation Of Basic And Diluted Net Loss Per Share) (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands

3 Months Ended

12 Months Ended

Dec. 31, 2016

Sep. 30, 2016

Jun. 30, 2016

Mar. 31, 2016

Dec. 31, 2015

Sep. 30, 2015

Jun. 30, 2015

Mar. 31, 2015

Dec. 31, 2014

Sep. 30, 2014

Jun. 30, 2014

Mar. 31, 2014

Dec. 31, 2016

Dec. 31, 2015

Dec. 31, 2014

Numerator:

Net loss

$ (2,522)

$ (3,518)

$ (3,015)

$ (5,795)

$ (4,517)

$ (3,671)

$ (3,374)

$ (2,583)

$ (2,156)

$ (3,534)

$ (3,246)

$ (3,450)

$ (14,850)

$ (14,145)

$ (12,386)

Denominator:

Shares used in computing net loss per share, basic and diluted

45,638

45,356

45,269

Net loss per share, basic and diluted

$ (0.06)

$ (0.08)

$ (0.07)

$ (0.13)

$ (0.10)

$ (0.08)

$ (0.07)

$ (0.06)

$ (0.05)

$ (0.08)

$ (0.07)

$ (0.08)

$ (0.33)

$ (0.31)

$ (0.27)

Dilutive common shares excluded from net loss per share, diluted

17,745

17,421

10,625