Fair Value of Financial Instruments Fair value by balance sheet grouping table (Tables)

3 Months Ended

Mar. 31, 2014

Fair Value Disclosures [Abstract]

Available-for-sale Securities

At March 31, 2014, we held $378 million of investments in fixed income securities with maturities ranging from less than one year to March 2017, compared to $373 million of investments in fixed income securities held at December 31, 2013. These securities are accounted for as available-for-sale and recorded at fair value as follows:

	March 31, 2014						December 31, 2013
Millions of dollars	Level 1		Level 2		Total		Level 1		Level 2		Total
Fixed income securities:
U.S. treasuries (a)	$	100	$	—	$	100	$	100	$	—	$	100
Other (b)	—		278		278		—		273		273
Total	$	100	$	278	$	378	$	100	$	273	$	373

(a) These securities are classified as "Other current assets" in our condensed consolidated balance sheets.

(b) Of these securities, $138 million are classified as “Other current assets” and $140 million are classified as “Other assets” on our condensed consolidated balance sheets as of March 31, 2014, compared to $139 million classified as “Other current assets” and $134 million classified as “Other assets” as of December 31, 2013. These securities consist primarily of municipal bonds, corporate bonds, and other debt instruments.

Schedule of Carrying Values and Estimated Fair Values of Debt Instruments

The carrying amount and fair value of our long-term debt is as follows:

	March 31, 2014								December 31, 2013
Millions of dollars	Level 1		Level 2		Total fair value		Carrying value		Level 1		Level 2		Total fair value		Carrying value
Long-term debt	$	8,712	$	294	$	9,006	$	7,816	$	8,405	$	292	$	8,697	$	7,816