Investments (Tables)

6 Months Ended

Jun. 30, 2018

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


	June 30, 2018		December 31, 2017
Available-for-sale investments:
Time deposits and certificates of deposit	$	18,455	$	9,757
Bankers’ acceptance drafts		2,522		5,330
Asset-backed securities		34,727		36,990
Commercial paper		25,925		13,750
Corporate obligations		66,663		77,821
Municipal bonds		2,615		1,970
U.S. treasury obligations		31,434		28,078
U.S. agency obligations		21,345		35,738

	$	203,686	$	209,434

Investments classified as long-term consist of the following:


	June 30, 2018		December 31, 2017
Available-for-sale investments:
Group insurance contracts	$	6,076	$	6,255
Cost method investments:
Minority interest in a private company		4,400		4,400

	$	10,476	$	10,655

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


As of June 30, 2018:	Cost		Gross Unrealized Gains		Gross Unrealized (Losses)			Estimated Fair Value
Short-term investments:
Available-for-sale investments:
Time deposits and certificates of deposit	$	18,452	$	3	$	—		$	18,455
Bankers’ acceptance drafts		2,522		—		—			2,522
Asset-backed securities		34,760		9		(42	)		34,727
Commercial paper		26,337		—		(412	)		25,925
Corporate obligations		66,632		59		(28	)		66,663
Municipal bonds		2,620		—		(5	)		2,615
U.S. treasury obligations		31,418		16		—			31,434
U.S. agency obligations		21,341		5		(1	)		21,345

	$	204,082	$	92	$	(488	)	$	203,686


As of June 30, 2018:	Cost		Gross Unrealized Gains		Gross Unrealized (Losses)			Estimated Fair Value
Long-term investments:
Available-for-sale investments:
Group insurance contracts	$	6,051	$	25	$	—		$	6,076


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