Investments

Investments at March 31, 2018 and December 31, 2017 consisted of mutual funds, United States corporate debt securities and an equity investment in the Company's affiliated entity PLS. Investments are recorded at fair value, based on current market valuations. After the adoption of ASU No. 2016-01 on January 1, 2018, unrealized gains and losses on the Company's equity securities are reported in the condensed consolidated statement of operations as non-operating other income (expense). Unrealized gains and losses on the Company's debt securities will continue to be excluded from earnings and are reported as a separate component of other comprehensive loss until realized. Realized gains and losses are included in non-operating other income (expense) on the condensed consolidated statement of operations and are derived using the specific identification method for determining the cost of the securities sold. During the three months ended March 31, 2018 and 2017, $253,000 and $52,000 of net realized loss on investments was recorded, respectively. The Company assessed each of its investments on an individual basis to determine if any decline in fair value was other-than-temporary. Interest and dividends on investments classified as available-for-sale are included in interest and other income, net, in the condensed consolidated statements of operations. As of March 31, 2018, the Company had 28 available-for-sale securities in a gross unrealized loss position, of which 3 with an aggregate total unrealized loss of $28,000 were in such position for longer than 12 months.

The following is a summary of available-for-sale securities as of March 31, 2018 and December 31, 2017:



		As of March 31, 2018
	Contractual Maturity (in years)	Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Market Value
Mutual funds	---	$	54,509,756	$	—	$	(306,308	)	$	54,203,448
US corporate debt securities	Less than 2	21,211,005		—		(154,564		)	21,056,441
Investment in affiliated entity (PLS)	---	—		3,307,192		—			3,307,192
Total investments		$	75,720,761	$	3,307,192	$	(460,872	)	$	78,567,081



		As of December 31, 2017
	Contractual Maturity (in years)	Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Market Value
Mutual funds	---	$	68,776,165	$	42,097	$	(252,373	)	$	68,565,889
US corporate debt securities	Less than 2	35,210,121		3,032		(140,198		)	35,072,955
Investment in affiliated entity (PLS)	---	—		2,325,079		—			2,325,079
Total investments		$	103,986,286	$	2,370,208	$	(392,571	)	$	105,963,923