Fair Value of Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2016

Fair Value Disclosures [Abstract]

Summary of Assets Measured at Fair Value on a Recurring Basis

The following table summarizes our investments measured at fair value on a recurring basis using the above input categories. As of September 30, 2016 and December 31, 2015, we did not hold any Level 3 assets, and our Level 1 and Level 2 holdings were as follows (in thousands):

	September 30, 2016						December 31, 2015
	Level 1		Level 2		Total		Level 1		Level 2		Total
Cash equivalents:
Money market funds	$	28,382	$	-	$	28,382	$	4,071	$	-	$	4,071
Commercial paper		-		-		-		-		999		999
Total cash equivalents		28,382		-		28,382		4,071		999		5,070
Investments:
Commercial paper		-		17,852		17,852		-		27,846		27,846
Corporate debt securities		-		17,936		17,936		-		45,830		45,830
Municipal bonds		-		2,511		2,511		-		1,433		1,433
Total investments		-		38,299		38,299		-		75,109		75,109
Total assets measured at fair    value	$	28,382	$	38,299	$	66,681	$	4,071	$	76,108	$	80,179

Carrying Value and Estimated Fair Value of Convertible Notes

The carrying value and estimated fair value of our Convertible Notes are as follows (in thousands):

	September 30, 2016				December 31, 2015
	Carrying Value		Estimated Fair Value		Carrying Value		Estimated Fair Value
Convertible notes	$	85,215	$	138,792	$	81,985	$	108,330