MARKETABLE SECURITIES

Our marketable securities consist of certificates of deposit, commercial paper, corporate bonds and government municipal bonds. We analyze our available-for-sale marketable securities for impairment on an ongoing basis. When we perform this analysis, we consider factors such as the length of time and extent to which the securities have been in an unrealized loss position and the trend of any unrealized losses. We also consider whether an unrealized loss is a temporary loss or an other-than-temporary loss based on factors such as: (a) whether we have the intent to sell the security, (b) whether it is more likely than not that we will be required to sell the security before its anticipated recovery, or (c) permanent impairment due to bankruptcy or insolvency.

In order to estimate the fair value for each security in our investment portfolio, we obtain quoted market prices and trading activity for each security where available. We obtain relevant information from our investment advisor and, if warranted, also may review the financial solvency of certain security issuers. As of December 31, 2017, 31 of our 41 securities that we held were trading below our amortized cost basis. We determined each decline in value to be temporary based upon the above described factors. We expect to realize the fair value of these securities, plus accrued interest, either at the time of maturity or when the security is sold. All of our current holdings are classified as available-for-sale marketable securities and are recorded at fair value on our consolidated balance sheet with the unrealized gains and losses recorded in accumulated other comprehensive income (loss). All of our current marketable securities will mature in less than one year and our non-current marketable securities will mature in less than two years. Our balance sheet classification of available for sale securities is based on our best estimate of when we expect to liquidate such investments and, presently, is consistent with the stated maturity dates of such investments. However, we are not committed to holding these investments until their maturity and may determine to liquidate some or all of these investments earlier based on our liquidity and other needs. During the three months ended December 31, 2017 and 2016, we received proceeds from our available-for-sale marketable securities of $4.3 million and $32.2 million, respectively.

At December 31, 2017 our marketable securities were (in thousands):



	Amortized Cost (1)		Unrealized Gains		Unrealized Losses			Fair Value (1)
Current marketable securities:
Corporate bonds	$	24,217	$	—	$	(26	)	$	24,191
Certificates of deposit	4,013		1		(1		)	4,013
Current marketable securities	28,230		1		(27		)	28,204
Non-current marketable securities:
Certificates of deposit	4,262		—		(15		)	4,247
Total marketable securities	$	32,492	$	1	$	(42	)	$	32,451


(1)	Included in amortized cost and fair value is purchased and accrued interest of $201.

6. MARKETABLE SECURITIES (CONTINUED)

At September 30, 2017 our marketable securities were (in thousands):



	Amortized Cost (1)		Unrealized Gains		Unrealized Losses			Fair Value (1)
Current marketable securities:
Corporate bonds	$	28,275	$	—	$	(20	)	$	28,255
Certificates of deposit	3,756		4		—			3,760
Current marketable securities	32,031		4		(20		)	32,015
Non-current marketable securities:
Certificates of deposit	4,757		—		(4		)	4,753
Total marketable securities	$	36,788	$	4	$	(24	)	$	36,768


(1)	Included in amortized cost and fair value is purchased and accrued interest of $211.

The following tables show the fair values and gross unrealized losses of our available-for-sale marketable securities that have been in a continuous unrealized loss position deemed to be temporary, aggregated by investment category (in thousands):



	December 31, 2017
	Less than 12 Months					More than 12 Months
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
Corporate bonds	$	24,191	$	(26	)	$	—	$	—
Certificates of deposit	5,754		(16		)	—		—
Total	$	29,945	$	(42	)	$	—	$	—



	September 30, 2017
	Less than 12 Months					More than 12 Months
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
Corporate bonds	$	26,196	$	(20	)	$	—	$	—
Certificates of deposit	3,751		(4		)	—		—
Total	$	29,947	$	(24	)	$	—	$	—