5)	Investments

The fair value of investments classified as short-term consists of the following:


	March 31, 2019		December 31, 2018
Available-for-sale investments:
Time deposits and certificates of deposit	$	101	$	102
Bankers’ acceptance drafts		1,722		989
Asset-backed securities		—		9,113
Commercial paper		33,509		19,359
Corporate obligations		8,994		9,352
U.S. treasury obligations		—		13,298
U.S. agency obligations		—		21,613

	$	44,326	$	73,826

Investments classified as long-term consist of the following:


	March 31, 2019		December 31, 2018
Available-for-sale investments:
Group insurance contracts	$	5,950	$	5,890
Cost method investments:
Minority interest in a private company		4,400		4,400

	$	10,350	$	10,290

The following tables show the gross unrealized gains and (losses) aggregated by investment category for available-for-sale investments:


As of March 31, 2019:	Cost		Gross Unrealized Gains		Gross Unrealized (Losses)			Estimated Fair Value
Short-term investments:
Available-for-sale investments:
Time deposits and certificates of deposit	$	99	$	2	$	—		$	101
Bankers’ acceptance drafts		1,722		—		—			1,722
Commercial paper		33,752		1		(244	)		33,509
Corporate obligations		8,996		1		(3	)		8,994

	$	44,569	$	4	$	(247	)	$	44,326


As of March 31, 2019:	Cost		Gross Unrealized Gains		Gross Unrealized (Losses)			Estimated Fair Value
Long-term investments:
Available-for-sale investments:
Group insurance contracts	$	5,582	$	368	$	—		$	5,950

As of December 31, 2018:	Cost		Gross Unrealized Gains		Gross Unrealized (Losses)			Estimated Fair Value
Short-term investments:
Available-for-sale investments:
Time deposits and certificates of deposit	$	102	$	—	$	—		$	102
Bankers’ acceptance drafts		989		—		—			989
Asset-backed securities		9,121		1		(9	)		9,113
Commercial paper		19,504		—		(145	)		19,359
Corporate obligations		9,367		—		(15	)		9,352
U.S. treasury obligations		13,294		4		—			13,298
U.S. agency obligations		21,617		2		(6	)		21,613

	$	73,994	$	7	$	(175	)	$	73,826


As of December 31, 2018:	Cost		Gross Unrealized Gains		Gross Unrealized (Losses)		Estimated Fair Value
Long-term investments:
Available-for-sale investments:
Group insurance contracts	$	5,546	$	344	$	—	$	5,890

The tables above, which show the gross unrealized gains and (losses) aggregated by investment category for available-for-sale investments as of March 31, 2019 and December 31, 2018, reflect the inclusion within short-term investments of investments with contractual maturities greater than one year from the date of purchase. Management has the ability, if necessary, to liquidate any of its investments in order to meet the Company’s liquidity needs in the next 12 months. Accordingly, those investments with contractual maturities greater than one year from the date of purchase are classified as short-term on the accompanying balance sheets.

The Company reviews and evaluates its investments for any indication of possible impairment. Based on this review, the Company has determined that the unrealized losses related to these investments at March 31, 2019 and December 31, 2018 were temporary.

Interest income is accrued as earned. Dividend income is recognized as income on the date the stock trades “ex-dividend.” The cost of marketable securities sold is determined by the specific identification method. Realized gains or losses are reflected in income and were not material for the three months ended March 31, 2019 and 2018.