Quarterly report pursuant to Section 13 or 15(d)

Balance Sheets Details (Details)

v2.4.0.6
Balance Sheets Details (Details) (USD $)
In Thousands, unless otherwise specified
3 Months Ended 12 Months Ended
Mar. 31, 2013
Dec. 31, 2012
Schedule of cash equivalents and marketable securities    
Adjusted Cost $ 32,436 $ 41,874
Gross Unrealized Gains 380 63
Gross Unrealized Losses 0 0
Estimated Fair Value 32,816 41,937
Money market funds [Member]
   
Schedule of cash equivalents and marketable securities    
Adjusted Cost 17,931 24,789
Gross Unrealized Gains 0 0
Gross Unrealized Losses 0 0
Estimated Fair Value 17,931 24,789
Commercial paper [Member]
   
Schedule of cash equivalents and marketable securities    
Adjusted Cost   1,499
Gross Unrealized Gains   1
Gross Unrealized Losses   0
Estimated Fair Value   1,500
Average Contractual Maturities (in days)   70 days
Corporate bonds [Member]
   
Schedule of cash equivalents and marketable securities    
Adjusted Cost 8,437 9,512
Gross Unrealized Gains 9 10
Gross Unrealized Losses   0
Estimated Fair Value 8,446 9,522
Average Contractual Maturities (in days) 82 days 156 days
U.S. Treasury obligations [Member]
   
Schedule of cash equivalents and marketable securities    
Adjusted Cost 5,505 5,511
Gross Unrealized Gains 4 5
Gross Unrealized Losses 0 0
Estimated Fair Value 5,509 5,516
Average Contractual Maturities (in days) 172 days 262 days
Common shares of CO2 Solution [Member]
   
Schedule of cash equivalents and marketable securities    
Adjusted Cost 563 563
Gross Unrealized Gains 367 47
Gross Unrealized Losses 0 0
Estimated Fair Value $ 930 $ 610