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

12 Months Ended

Dec. 31, 2011

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

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

	Estimated Fair Value at
	December 31, 2011		December 31, 2010
Cash and cash equivalents	$	15,312	$	17,755
Short-term investments		225,856		298,177
Long-term investments		173,768		—
Total cash, cash equivalents, and available-for-sale investments	$	414,936	$	315,932

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

	Estimated Fair Value at
	December 31, 2011		December 31, 2010
Corporate notes and bonds	$	344,427	$	190,527
U.S. corporate commercial paper		9,464		82,361
Obligations of U.S. government agencies		44,230		25,289
Obligations of U.S. states and municipalities		1,503		—
Cash and money market funds		15,312		17,755
Total cash, cash equivalents, and available-for-sale investments	$	414,936	$	315,932

Portfolio of available-for-sale investments

	Estimated Fair Value at
	December 31, 2011		December 31, 2010
Less than one year	$	213,386	$	298,177
Greater than one year but less than two years		186,238		—
Total available-for-sale investments	$	399,624	$	298,177

Financial assets measured at fair value on a recurring basis

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

As of December 31, 2010:	Level 1		Level 2		Level 3		Total
Money market funds	$	16,028	$	—	$	—	$	16,028
U.S. corporate commercial paper		—		82,361		—		82,361
Corporate notes and bonds		—		190,527		—		190,527
Obligations of U.S. government agencies		—		25,289		—		25,289
Cash equivalents and available-for-sale investments	$	16,028	$	298,177	$	—	$	314,205
Cash								1,727
Cash, cash equivalents, and available-for-sale investments							$	315,932

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.