Marketable Securities

9 Months Ended

Sep. 30, 2013

Investments, Debt and Equity Securities [Abstract]

Marketable Securities

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 loss on our consolidated balance sheets. Proceeds received from sales and maturities of marketable securities were $144 million for the nine months ended September 30, 2013. Our investments in marketable securities consisted of the following:

	As of September 30, 2013				As of December 31, 2012
(millions)	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Corporate debt securities	$	88	$	88	$	82	$	82
U.S. government and agency debt securities	11		11		16		16
Non-U.S. government debt securities	—		—		1		1
Asset-backed debt securities	14		14		6		6
Certificates of deposit	17		17		16		16
Municipal debt securities	8		8		10		10
Total marketable securities	$	138	$	138	$	131	$	131

The realized and unrealized gains and losses for the three months and nine months ended September 30, 2013 and 2012 and the year ended December 31, 2012 were immaterial. Cost basis for securities sold are determined on a first-in-first-out basis.

Contractual maturities of marketable securities as of September 30, 2013 were as follows:

(millions)	Amortized Cost		Fair Value
Due in 1 year or less	$	100	$	100
Due in 1-5 years	38		38
Total marketable securities	$	138	$	138

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