Debt

Debt consists of (in millions):


	March 31,		December 31,
	2015		2014

Senior Notes, interest at 6.125% payable semiannually, principal due on August 15, 2015	$	151	$	151

Senior Notes, interest at 1.35% payable semiannually, principal due on December 1, 2017		500		500

Senior Notes, interest at 2.6% payable semiannually, principal due on December 1, 2022		1,396		1,396

Senior Notes, interest at 3.95% payable semiannually, principal due on December 1, 2042		1,096		1,096

Commercial paper		1,080		—

Other		22		23

Total debt		4,245		3,166
Less current portion		151		152

Long-term debt	$	4,094	$	3,014

The Company has a $3.5 billion, five-year unsecured revolving credit facility which expires September 28, 2018. The Company also has a commercial paper program. Borrowings under the commercial paper program are classified as long-term as the program is supported by the $3.5 billion, five-year revolving credit facility. At March 31, 2015, there were $1,080 million in commercial paper borrowings, and there were $438 million in outstanding letters of credit issued under the credit facility, resulting in $1,982 million of funds available under this revolving credit facility. Interest under this multicurrency facility is based upon LIBOR, NIBOR or EURIBOR plus 0.875% subject to a ratings-based grid, or the U.S. prime rate. The credit facility contains a financial covenant regarding maximum debt to capitalization and the Company was in compliance at March 31, 2015.

The Company also had $3,386 million of additional outstanding letters of credit at March 31, 2015, primarily in Norway, that are under various bilateral committed letter of credit facilities. Other letters of credit are issued as bid bonds, advanced payment bonds and performance bonds.

The fair value of the Company’s debt is estimated using Level 2 inputs in the fair value hierarchy and is based on quoted prices for those or similar instruments. At March 31, 2015 and December 31, 2014, the fair value of the Company’s unsecured Senior Notes approximated $3,064 million and $2,974 million, respectively. At both March 31, 2015 and December 31, 2014, the carrying value of the Company’s unsecured Senior Notes approximated $3,143 million. The carrying value of the Company’s variable rate borrowings approximates fair value.