Fair value of financial instruments (Tables)

9 Months Ended

Sep. 30, 2013

Fair Value Disclosures [Abstract]

Summary of Fair Value Measurement of Financial Instruments

The following table presents information about the Company’s financial instruments that are measured at fair value as of September 30, 2013 and indicates the fair value hierarchy of the valuation (in thousands):

	Total		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)
Description
Cash equivalents:
Money market mutual funds	$	142,968	$	142,968	$	—
Total cash equivalents	142,968		142,968		—
Short-term investments:
Corporate bonds	39,555		—		39,555
U.S. agency securities	32,274		—		32,274
Asset-backed securities	13,957		—		13,957
U.S. Treasury securities	17,818		—		17,818
Total short-term investments	103,604		—		103,604
Cash equivalents and short-term investments	$	246,572	$	142,968	$	103,604

The following table presents information about the Company’s financial instruments that are measured at fair value as of December 31, 2012 and indicates the fair value hierarchy of the valuation (in thousands):

	Total		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)
Description
Cash equivalents:
Money market mutual funds	$	17,000	$	17,000	$	—
Total cash equivalents	17,000		17,000		—
Short-term investments:
Corporate bonds	13,377		—		13,377
U.S. agency securities	11,283		—		11,283
Asset-backed securities	4,666		—		4,666
U.S. Treasury securities	3,548		—		3,548
Total short-term investments	32,874		—		32,874
Cash equivalents and short-term investments	$	49,874	$	17,000	$	32,874