Stock Options (Details)	12 Months Ended	0 Months Ended
	Dec. 31, 2014 item	May 17, 2012	May 19, 2011	May 20, 2010	May 21, 2009	May 29, 2008	May 30, 2007	Dec. 31, 2013	Dec. 31, 2012	Mar. 22, 2005	Dec. 31, 2001	Dec. 31, 1995	Mar. 17, 2005
Stock Options
Number of stock-based compensation plans	2
Options outstanding (in shares)	3,076,000							3,045,000	2,779,000
Common shares reserved for future issuance								4,423,407
Option exercisable period one	1 year
Option exercisable period three	3 years
Option exercisable period three	5 years
Expiration term	10 years
Expiration term for incentive stock options granted to holders of more than 10% of the entity's voting stock	5 years
Maximum
Stock Options
Exercise price as a percentage of the fair market value of common stock in case of optionees holding more than 10% of voting stock	110.00%
Minimum
Stock Options
Voting stock percentage to be held by optionees	10.00%
PREFERRED STOCK
Stock Options
Common shares reserved for future issuance	1,067,000
1995 Plan
Stock Options
Shares available for issuance											825,000	400,000
Shares available for future grant										0
Options exercised (in shares)	67,365
Options outstanding (in shares)	138,800
Common shares reserved for future issuance	139,000
2005 Plan
Stock Options
Shares available for issuance		3,700,000	3,400,000	3,000,000	2,500,000		1,500,000						750,000
Shares available for future grant	280,164
Additional increase in number of shares available for issuance		300,000	400,000	500,000	500,000	500,000	750,000
Number of separate equity incentive programs	3
Options exercised (in shares)	482,835
Options outstanding (in shares)	2,937,001
Options granted (in shares)	3,852,000
Options cancelled (in shares)	432,164
Shares issued pursuant to the Stock Issuance Program	0
Common shares reserved for future issuance	3,217,000
2005 Plan | Non-employee Board member
Stock Options
Options that will be granted upon initial election or appointment to the Board (in shares)	10,000
Preceding period within which individual has not previously been employed by the company	6 months
Options that will be granted to purchase shares of common stock on the date of each annual stockholders meeting	5,000
Period for which individual should serve as a non-employee Board member	6 months