7. Debt

Debt consists of (in millions):


	June 30, 2013		December 31, 2012
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		1,395		1,395
Senior Notes, interest at 3.95% payable semiannually, principal due on December 1, 2042		1,096		1,096
Revolving Credit Facility, expires September 28, 2017		970		—
Other		8		7

Total debt		4,120		3,149
Less current portion		—		1

Long-term debt	$	4,120	$	3,148

The Company has a $3.5 billion, five-year unsecured revolving credit facility which expires September 28, 2017. At June 30, 2013, there were $970 million in outstanding borrowings against the credit facility, and there were $858 million in outstanding letters of credit issued under the credit facility, resulting in $1,672 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 prime rate. The credit facility contains a financial covenant regarding maximum debt to capitalization and the Company was in compliance at June 30, 2013.

The Company also had $2,641 million of additional outstanding letters of credit at June 30, 2013, primarily in Norway, that are under various bilateral committed letter of credit facilities. Other letters of credit are issued as bid bonds and performance bonds.

The fair value of the Company’s Senior Notes are estimated using Level 2 inputs in the fair value hierarchy and is based on quoted prices for those or similar instruments. At June 30, 2013 and December 31, 2012, the fair value of the Company’s unsecured Senior Notes approximated $2,938 million and $3,190, respectively. At June 30, 2013 and December 31, 2012, the carrying value of the Company’s unsecured Senior Notes was $3,142 million. The carrying value of the Company’s variable rate borrowings approximates fair value.