Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2013

Fair Value Measurements

Schedule of fair value hierarchy about each major category of financial assets and liabilities measured at fair value on a recurring basis

	Fair Value Measurement at June 30, 2013 using:
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Balance as of June 30, 2013
Assets
Cash equivalents	$	24,223,000	$	—	$	—	$	24,223,000
U.S. government agency securities	—		3,996,000		—		3,996,000
Corporate debt securities	—		27,960,000		—		$	27,960,000
Total	$	24,223,000	$	31,956,000	$	—	$	56,179,000

	Fair Value Measurement at December 31, 2012 using:
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Balance as of December 31, 2012
Assets:
Cash equivalents	$	71,316,000	$	—	$	—	$	71,316,000
Total	$	71,316,000	$	—	$	—	$	71,316,000