Fair Value Measurements (Details) (Recurring basis [Member], USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Cash equivalents:
Total cash equivalents	$ 8,192	$ 7,077
Short-term investments:
Total short-term investments	9,402	9,619
Total assets	18,469	17,571
MPC earn-out liability	696	766
Money market funds [Member]
Cash equivalents:
Total cash equivalents	7,442	6,576
Short-term investments:
Restricted cash-money market fund	875	875
Corporate debt [Member]
Cash equivalents:
Total cash equivalents	750	501
U.S. agency securities [Member]
Short-term investments:
Total short-term investments		1,751
Municipal securities [Member]
Short-term investments:
Total short-term investments	355	355
Corporate commercial paper [Member]
Short-term investments:
Total short-term investments	2,299	1,250
Foreign government bonds [Member]
Short-term investments:
Total short-term investments	501	500
Corporate debt [Member]
Short-term investments:
Total short-term investments	6,247	5,763
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Cash equivalents:
Total cash equivalents	7,442	6,576
Short-term investments:
Total short-term investments
Total assets	8,317	7,451
MPC earn-out liability
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Money market funds [Member]
Cash equivalents:
Total cash equivalents	7,442	6,576
Short-term investments:
Restricted cash-money market fund	875	875
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Corporate debt [Member]
Cash equivalents:
Total cash equivalents
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Municipal securities [Member]
Short-term investments:
Total short-term investments
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Corporate commercial paper [Member]
Short-term investments:
Total short-term investments
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Foreign government bonds [Member]
Short-term investments:
Total short-term investments
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Corporate debt [Member]
Short-term investments:
Total short-term investments
Direct or Indirect Observable Inputs (Level 2) [Member]
Cash equivalents:
Total cash equivalents	750	501
Short-term investments:
Total short-term investments	9,402	9,619
Restricted cash-money market fund
Total assets	10,152	10,120
MPC earn-out liability
Direct or Indirect Observable Inputs (Level 2) [Member] | Money market funds [Member]
Cash equivalents:
Total cash equivalents
Direct or Indirect Observable Inputs (Level 2) [Member] | Corporate debt [Member]
Cash equivalents:
Total cash equivalents	750	501
Direct or Indirect Observable Inputs (Level 2) [Member] | U.S. agency securities [Member]
Short-term investments:
Total short-term investments		1,751
Direct or Indirect Observable Inputs (Level 2) [Member] | Municipal securities [Member]
Short-term investments:
Total short-term investments	355	355
Direct or Indirect Observable Inputs (Level 2) [Member] | Corporate commercial paper [Member]
Short-term investments:
Total short-term investments	2,299	1,250
Direct or Indirect Observable Inputs (Level 2) [Member] | Foreign government bonds [Member]
Short-term investments:
Total short-term investments	501	500
Direct or Indirect Observable Inputs (Level 2) [Member] | Corporate debt [Member]
Short-term investments:
Total short-term investments	6,247	5,763
Significant Unobservable Inputs (Level 3) [Member]
Cash equivalents:
Total cash equivalents
Short-term investments:
Total short-term investments
Restricted cash-money market fund
Total assets
MPC earn-out liability	696	766
Significant Unobservable Inputs (Level 3) [Member] | Money market funds [Member]
Cash equivalents:
Total cash equivalents
Significant Unobservable Inputs (Level 3) [Member] | Corporate debt [Member]
Cash equivalents:
Total cash equivalents
Significant Unobservable Inputs (Level 3) [Member] | Municipal securities [Member]
Short-term investments:
Total short-term investments
Significant Unobservable Inputs (Level 3) [Member] | Corporate commercial paper [Member]
Short-term investments:
Total short-term investments
Significant Unobservable Inputs (Level 3) [Member] | Foreign government bonds [Member]
Short-term investments:
Total short-term investments
Significant Unobservable Inputs (Level 3) [Member] | Corporate debt [Member]
Short-term investments:
Total short-term investments