Fair Value (Tables)

12 Months Ended

Dec. 31, 2011

Fair Value [Abstract]

Schedule Of Financial Assets By Level Within The Fair Value Hierarchy

	Fair value measurement using:
	Quoted prices in active markets for identical assets (Level 1)		Other observable inputs (Level 2)		Significant unobservable inputs (Level 3)		Total
As of December 31, 2011
Cash equivalents—money market funds	$	66	$	0	$	0	$	66
Short-term investments:
U.S. Treasury securities		227,718		0		0		227,718
Corporate obligations		0		9,564		0		9,564
Auction rate securities		0		0		5,780		5,780
Other non-current assets—U.S. Treasury securities		304		0		0		304
Total	$	228,088	$	9,564	$	5,780	$	243,432
	Fair value measurement using:
	Quoted prices in active markets for identical assets (Level 1)		Other observable inputs (Level 2)		Significant unobservable inputs (Level 3)		Total
As of December 31, 2010
Cash equivalents—money market funds	$	10,613	$	0	$	0	$	10,613
Short-term investments:
U.S. Treasury securities		249,276		0		0		249,276
Corporate obligations		0		11,406		0		11,406
Long-term investments—auction rate securities		0		0		13,031		13,031
Other non-current assets—U.S. Treasury securities		303		0		0		303
Total	$	260,192	$	11,406	$	13,031	$	284,629

Schedule Of Auction Rate Securities Where Fair Value Is Determined Using Level 3 Inputs

	December 31,
	2011			2010
Balance, beginning of year	$	13,031		$	12,459
Unrealized gain (loss) included in other comprehensive income (loss)		(240	)		572
Losses deemed other than temporary reclassified from other comprehensive loss		1,659			0
Impairment losses included in interest income (loss), net		(8,670	)		0
Balance, end of year	$	5,780		$	13,031