Marketable Securities (Tables)

9 Months Ended

Sep. 30, 2011

Marketable Securities [Abstract]

Investments in marketable securities as available for sale

	September 30, 2011
	Amortized		Unrealized			Market
	Cost		Gain (Loss)			Value
	(In thousands)
U.S. Treasury Bills (due within one year)	$	801,543	$	(79	)	$	801,464
Mortgage-backed securities		425		42			467
Total	$	801,968	$	(37	)	$	801,931

	December 31, 2010
	Amortized		Unrealized		Market
	Cost		Gain		Value
	(In thousands)
U.S. Treasury Bills (due within one year)	$	599,965	$	15	$	599,980
Corporate bonds		11,200		560		11,760
Mortgage-backed securities		553		53		606
Total	$	611,718	$	628	$	612,346

Summary of proceeds from sales and maturities of marketable securities and gross realized gains and losses

	Three Months Ended						Nine Months Ended
	September 30,						September 30,
	2011			2010			2011			2010
	(In thousands)
Proceeds from sales	$	19		$	88		$	12,108		$	176
Proceeds from maturities		1,550,000			1,150,000			4,850,000			3,700,000
Gross realized gains		—			—			784			—
Gross realized losses		(1	)		(3	)		(3	)		(5	)