3)	Investments

The fair value of short-term investments with maturities or estimated lives of less than one year consists of the following:


	March 31, 2015		December 31, 2014
Available-for-sale investments:
Time deposits and certificates of deposit	$	5,400	$	20,900
Bankers’ acceptance drafts		327		82
Commercial paper		1,447		—
Corporate obligations		58,331		24,020
Municipal bonds		5,798		2,099
U.S. agency obligations		87,328		82,493

	$	158,631	$	129,594

The fair value of long-term investments with maturities of more than one year consists of the following:


	March 31, 2015		December 31, 2014
Available-for-sale investments:
Time deposits and certificates of deposit	$	—	$	48
Asset-backed securities		129,242		75,674
Corporate obligations		90,114		64,669
Municipal bonds		1,880		1,254
U.S. agency obligations		16,077		15,556

	$	237,313	$	157,201

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


As of March 31, 2015:	Cost		Gross Unrealized Gains		Gross Unrealized (Losses)			Estimated Fair Value
Short-term investments:
Time deposits and certificates of deposit	$	5,400	$	—	$	—		$	5,400
Bankers’ acceptance drafts		327		—		—			327
Commercial paper		1,447		—		—			1,447
Corporate obligations		58,336		10		(15	)		58,331
Municipal bonds		5,800		1		(3	)		5,798
U.S. agency obligations		87,311		23		(6	)		87,328

	$	158,621	$	34	$	(24	)	$	158,631

Long-term investments:
Asset-backed securities		129,209	$	66	$	(33	)	$	129,242
Corporate obligations		90,128		44		(58	)		90,114
Municipal bonds		1,878		3		(1	)		1,880
U.S. agency obligations		16,070		8		(1	)		16,077

	$	237,285	$	121	$	(93	)	$	237,313


As of December 31, 2014:	Cost		Gross Unrealized Gains		Gross Unrealized (Losses)			Estimated Fair Value
Short-term investments:
Time deposits and certificates of deposit	$	20,901	$	—	$	(1	)	$	20,900
Bankers’ acceptance drafts		82		—		—			82
Corporate obligations		24,029		2		(11	)		24,020
Municipal bonds		2,100		—		(1	)		2,099
U.S. agency obligations		82,488		14		(9	)		82,493

	$	129,600	$	16	$	(22	)	$	129,594

Long-term investments:
Time deposits and certificates of deposit	$	48	$	—	$	—		$	48
Asset-backed securities		75,778		5		(109	)		75,674
Corporate obligations		64,842		1		(174	)		64,669
Municipal bonds		1,258		—		(4	)		1,254
U.S. agency obligations		15,563		2		(9	)		15,556

	$	157,489	$	8	$	(296	)	$	157,201

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 immaterial for the three months ended March 31, 2015 and 2014.

In accordance with the Company’s investment policy, no security shall have a maturity or average life longer than three years. The average duration of the portfolio shall be no more than one year. Corporate securities must have ratings of A3/A- or better. Asset-backed securities must be rated AAA. Short-term ratings of A-2/P2/F2 or higher are also permitted. With respect to compliance with these investment guidelines, the rating agencies include Moody’s Investor Service, Standard & Poor’s and Fitch Investor Service. The middle of Moody’s, Standard & Poor’s and Fitch rating shall be used to determine compliance with credit quality guidelines. If a security is rated by two rating agencies, the lower rating will apply. If only one rating exists, that rating shall be used.