Fair Value (Tables)

9 Months Ended

Sep. 30, 2011

Fair Value [Abstract]

Fair Value Measurement Of Financial Assets

			Fair Value Measurements at Reporting Date Using
			(Level 1)		(Level 2)		(Level 3)
Description	As of September 30, 2011		Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
Cash equivalents:
Money market funds		$167,993		$167,993		$0		$0
Short-term investments:
U.S. Treasury obligations		90,629		90,629		0		0
Government agency obligations		31,565		0		31,565		0
Corporate obligations		24,605		0		24,605		0
Other assets:
Money market fund		7,307		7,307		0		0
		$322,099		$265,929		$56,170		$0