Investments (Tables)

3 Months Ended

Mar. 31, 2013

Investments Debt And Equity Securities [Abstract]

Fair Value of Available for Sale and Trading Investments

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

	March 31, 2013		December 31, 2012
Available-for-sale investments:
Time deposits	$	—	$	52
Bankers’ acceptance drafts		93		242
U.S. treasury obligations		13,042		13,054
U.S. agency obligations		317,686		313,514
	$	330,821	$	326,862
Trading investments:
Mutual funds		813		791
	$	331,634	$	327,653

Fair Value of Long-Term Available-for-Sale Investments

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

	March 31, 2013		December 31, 2012
Time deposits	$	53	$	—
U.S. agency obligations		10,104		12,158
	$	10,157	$	12,158

Gross Unrealized Gains and (Losses) Aggregated by Investment Category Short-Term and Long-Term Securities

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

	Cost		Gross Unrealized Gains		Gross Unrealized (Losses)			Estimated Fair Value
As of March 31, 2013:
Short-term investments:
Bankers’ acceptance drafts	$	93	$	—	$	—		$	93
U.S. treasury obligations		13,036		6		—			13,042
U.S. agency obligations		317,517		171		(2	)		317,686
	$	330,646	$	177	$	(2	)	$	330,821
Long-term investments:
Time deposits	$	53	$	—	$	—		$	53
U.S. agency obligations		10,099		5		—			10,104
	$	10,152	$	5	$	—		$	10,157

	Cost		Gross Unrealized Gains		Gross Unrealized (Losses)			Estimated Fair Value
As of December 31, 2012:
Short-term investments:
Time deposits	$	52	$	—	$	—		$	52
Bankers’ acceptance drafts		242		—		—			242
U.S. treasury obligations		13,045		9		—			13,054
U.S. agency obligations		313,262		258		(6	)		313,514
	$	326,601	$	267	$	(6	)	$	326,862
Long-term investments:
U.S. agency obligations	$	12,156	$	2	$	—		$	12,158