Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2012

Investments in Marketable Securities as Available For Sale

Our investments in marketable securities are classified as available for sale and are summarized as follows:

	December 31, 2012
	Amortized Cost		Unrealized Gain (Loss)		Market Value
	(In thousands)
U.S. Treasury Bills and Notes     (due within one year)	$	1,149,707	$	150	$	1,149,857
Mortgage-backed securities		276		25		301
Total	$	1,149,983	$	175	$	1,150,158

	December 31, 2011
	Amortized Cost		Unrealized Gain (Loss)			Market Value
	(In thousands)
U.S. Treasury Bills and Notes     (due within one year)	$	902,042	$	(59	)	$	901,983
Mortgage-backed securities		394		37			431
Total	$	902,436	$	(22	)	$	902,414

Summary of Proceeds From Sale and Maturities of Marketable Securities and Gross Realized Gains and Losses

Proceeds from maturities and sales of marketable securities and gross realized gains and losses are summarized as follows:

	Year Ended December 31,
	2012			2011			2010
	(In thousands)
Proceeds from maturities	$	2,575,000		$	5,350,000		$	5,450,000
Proceeds from sales		150,118			12,138			230
Gross realized gains		--			784			0
Gross realized losses		(6	)		(5	)		(7)