Cash, Cash Equivalents, and Available-For-Sale Investments (Tables)

3 Months Ended

Mar. 31, 2012

Cash, Cash Equivalents, and Available-For-Sales Investments [Abstract]

Cash, cash equivalents, and available-for-sale investments

	Estimated Fair Value at
	March 31, 2012		December 31, 2011
Cash and cash equivalents	$	148,485	$	15,312
Short-term investments		233,624		225,856
Long-term investments		116,732		173,768
Total cash, cash equivalents, and available-for-sale investments	$	498,841	$	414,936

Portfolio of cash, cash equivalents, and available-for-sale investments

	Estimated Fair Value at
	March 31, 2012		December 31, 2011
Corporate notes and bonds	$	310,389	$	344,427
U.S. corporate commercial paper		24,456		9,464
Obligations of U.S. government agencies		14,003		44,230
Obligations of U.S. states and municipalities		1,508		1,503
Cash and money market funds		148,485		15,312
Total cash, cash equivalents, and available-for-sale investments	$	498,841	$	414,936

Portfolio of available-for-sale investments by contractual maturity

	Estimated Fair Value at
	March 31, 2012		December 31, 2011
Less than one year	$	233,624	$	213,386
Greater than one year but less than two years		116,732		186,238
Total available-for-sale investments	$	350,356	$	399,624

Financial assets measured at fair value on a recurring basis

As of March 31, 2012:	Level 1		Level 2		Level 3		Total
Money market funds	$	147,515	$	—	$	—	$	147,515
U.S. corporate commercial paper		—		24,456		—		24,456
Corporate notes and bonds		—		310,389		—		310,389
Obligations of U.S. government agencies		—		14,003		—		14,003
Obligations of U.S. states and municipalities		—		1,508		—		1,508
Cash equivalents and available-for-sale investments	$	147,515	$	350,356	$	—	$	497,871
Cash								970
Cash, cash equivalents, and available-for-sale investments							$	498,841

As of December 31, 2011:	Level 1		Level 2		Level 3		Total
Money market funds	$	13,950	$	—	$	—	$	13,950
U.S. corporate commercial paper		—		9,464		—		9,464
Corporate notes and bonds		—		344,427		—		344,427
Obligations of U.S. government agencies		—		44,230		—		44,230
Obligations of U.S. states and municipalities		—		1,503		—		1,503
Cash equivalents and available-for-sale investments	$	13,950	$	399,624	$	—	$	413,574
Cash								1,362
Cash, cash equivalents, and available-for-sale investments							$	414,936

Level 1 —	Quoted prices in active markets for identical assets or liabilities.
Level 2 —	Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.
Level 3 —	Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.