Investments (Tables)

3 Months Ended

Mar. 31, 2013

Investments

Summary of Short-term investments

Short-term investments as of December 31, 2012 are summarized as follows:

	Amortized Cost		Gross Unrealized Losses			Estimated Fair Value
Municipal bonds & notes	$	23,755	$	(105	)	$	23,650
Corporate bonds	4,557		(53		)	4,504
Total available-for-sale securities	28,312		(158		)	28,154
Certificate of deposits	10,021		—			10,021
Total short-term investments	$	38,333	$	(158	)	$	38,175

Short-term investments as of March 31, 2013 are summarized as follows:

	Amortized Cost		Gross Unrealized Losses		Estimated Fair Value
Municipal bonds & notes	$	23,698	(158	)	$	23,540
Zero coupon bonds	124		—		124
Corporate bonds	4,277		(37	)	4,240
Total available-for-sale securities	28,099		(195	)	27,904
Certificate of deposits	10,062		—		10,062
Total short-term investments	$	38,161	(195	)	$	37,966