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Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2011

Marketable Securities

Cash equivalents and marketable securities classified as available-for-sale

		As of December 31, 2011
(Dollars in thousands)		Fair Value			Amortized Cost			Gross Unrealized Gains			Gross Unrealized Losses			Weighted Rate of Return
Money market funds		$	127,559		$	127,559		$	—		$	—			0.01	%
Corporate notes, bonds and commercial paper			137,108			137,208			—			(100	)		0.29	%
Total cash equivalents and marketable securities			264,667			264,767			—			(100	)
Cash			24,789			24,789			—			—
Total cash, cash equivalents and marketable securities		$	289,456		$	289,556		$	—		$	(100	)

		As of December 31, 2010
(Dollars in thousands)		Fair Value			Amortized Cost			Gross Unrealized Gains			Gross Unrealized Losses			Weighted Rate of Return
Money market funds		$	132,364		$	132,364		$	—		$	—			0.04	%
U.S. government sponsored obligations			266,817			266,840			29			(52	)		0.26	%
Corporate notes, bonds and commercial paper			95,724			95,773			8			(57	)		0.39	%
Total cash equivalents and marketable securities			494,905			494,977			37			(109	)
Cash			17,104			17,104			—			—
Total cash, cash equivalents and marketable securities		$	512,009		$	512,081		$	37		$	(109	)

Available-for-sale securities reported at fair value

		As of
		December 31, 2011			December 31, 2010
		(Dollars in thousands)
Cash equivalents		$	137,455		$	198,158
Short term marketable securities			127,212			296,747
Total cash equivalents and marketable securities			264,667			494,905
Cash			24,789			17,104
Total cash, cash equivalents and marketable securities		$	289,456		$	512,009

Estimated fair value of cash equivalents and marketable securities classified by date of contractual maturity and the length of time that the securities have been in a continuous unrealized loss position

		As of						Unrealized Loss, net
		December 31, 2011			December 31, 2010			December 31, 2011			December 31, 2010
		(In thousands)
Less than one year		$	264,667		$	494,905		$	(100	)	$	(72	)

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