Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2013

Cash Equivalents and Investments Classified as Available-for-sale Securities

Cash equivalents, and investments, all of which are classified as available-for-sale securities, consisted of the following (in thousands):

	September30, 2013													December31, 2012
	Cost			Unrealized Gains			Unrealized Losses				Estimated FairValue				Cost			Unrealized Gains			Unrealized Losses				Estimated FairValue
Money market funds	$	54,929	$		—	$		—		$		54,929	$			43,303	$		—	$		—		$		43,303
Corporate notes and commercial paper		103,034			40			(7	)			103,067				64,403			25			(3	)			64,425
U.S. government agency securities		57,119			34			(3	)			57,150				19,335			11			—				19,346
	$	215,082	$		74	$		(10	)	$		215,146	$			127,041	$		36	$		(3	)	$		127,074
Classified as:
Cash equivalents										$		54,929												$		43,303
Short-term investments												116,066														77,656
Long-term investments												44,151														6,115
Total cash equivalents and investments										$		215,146												$		127,074