Investments (Tables)

3 Months Ended

Mar. 31, 2018

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


	March 31, 2018		December 31, 2017
Available-for-sale investments:
Time deposits and certificates of deposit	$	10,459	$	9,757
Bankers’ acceptance drafts		2,179		5,330
Asset-backed securities		38,012		36,990
Commercial paper		16,010		13,750
Corporate obligations		78,767		77,821
Municipal bonds		2,618		1,970
U.S. treasury obligations		30,220		28,078
U.S. agency obligations		22,349		35,738

	$	200,614	$	209,434

Investments classified as long-term consist of the following:


	March 31, 2018		December 31, 2017
Available-for-sale investments:
Group insurance contracts	$	6,441	$	6,255
Cost method investments:
Minority interest in a private company		4,400		4,400

	$	10,841	$	10,655

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


As of March 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	$	10,458	$	1	$	—		$	10,459
Bankers’ acceptance drafts		2,179		—		—			2,179
Asset-backed securities		38,056		13		(57	)		38,012
Commercial paper		16,065		—		(55	)		16,010
Corporate obligations		78,778		38		(49	)		78,767
Municipal bonds		2,620		—		(2	)		2,618
U.S. treasury obligations		30,196		24		—			30,220
U.S. agency obligations		22,343		6		—			22,349

	$	200,695	$	82	$	(163	)	$	200,614


As of March 31, 2018:	Cost		Gross Unrealized Gains		Gross Unrealized (Losses)		Estimated Fair Value
Long-term investments:
Available-for-sale investments:
Group insurance contracts	$	6,382	$	59	$	—	$	6,441


As of December 31, 2017:	Cost		Gross Unrealized Gains		Gross Unrealized (Losses)			Estimated Fair Value
Short-term investments:
Available-for-sale investments:
Time deposits and certificates of deposit	$	9,756	$	1	$	—		$	9,757
Bankers acceptance drafts		5,330		—		—			5,330
Asset-backed securities		37,017		15		(42	)		36,990
Commercial paper		13,810		—		(60	)		13,750
Corporate obligations		77,788		58		(25	)		77,821
Municipal bonds		1,970		—		—			1,970
U.S. treasury obligations		28,054		24		—			28,078
U.S. agency obligations		35,728		10		—			35,738

	$	209,453	$	108	$	(127	)	$	209,434


As of December 31, 2017:	Cost		Gross Unrealized Gains		Gross Unrealized (Losses)		Estimated Fair Value
Long-term investments:
Available-for-sale investments:
Group insurance contracts	$	6,006	$	249	$	—	$	6,255