Marketable Securities

6 Months Ended

Jun. 30, 2011

Marketable Securities [Abstract]

Marketable Securities

6. Marketable Securities

Marketable securities are classified as available-for-sale securities and reported at fair value, with unrealized gains and losses excluded from earnings and reported in accumulated other comprehensive income (loss), or AOCI, on our condensed consolidated balance sheets. The realized and unrealized gains and losses as of and for the quarter ended June 30, 2011 were immaterial. Proceeds received from sales and maturities of marketable securities were $176 million for the six months ended June 30, 2011. Our investments in marketable securities as of June 30, 2011 consisted of the following:

	Amortized		Fair
(millions)	Cost		Value
Corporate debt securities	$	167	$	167
U.S. government and agency debt securities		63		63
Asset-backed debt securities		18		18
Certificates of deposit		49		49
Municipal debt securities		26		26
Total marketable securities	$	323	$	323

     Contractual maturities of marketable securities as of June 30, 2011 were as follows:

	Amortized		Fair
(millions)	Cost		Value
Due in 1 year or less	$	158	$	158
Due in 1-5 years		165		165
Due in more than 5 years		—		—
Total marketable securities	$	323	$	323

     Actual maturities may differ from the contractual maturities because issuers of the securities may have the right to prepay them.