7. Debt

Debt consists of (in millions):


	March 31, 2016		December 31, 2015
Senior Notes, interest at 1.35% payable semiannually, principal due on December 1, 2017	$	499	$	498
Senior Notes, interest at 2.60% payable semiannually, principal due on December 1, 2022		1,390		1,389
Senior Notes, interest at 3.95% payable semiannually, principal due on December 1, 2042		1,087		1,087
Commercial paper		207		890
Other		196		45

Total debt		3,379		3,909
Less current portion		7		2

Long-term debt	$	3,372	$	3,907

On January 1, 2016, the Company adopted Accounting Standards Update (“ASU”) No. 2015-03 “Simplifying the Presentation of Debt Issuance Costs.” This ASU requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. We have applied the change retrospectively for prior period balances of unamortized debt issuance costs, resulting in a $21 million reduction in other assets and long-term debt on our consolidated balance sheet as of December 31, 2015. The table above now presents our debt liability net of the related debt discount and debt issuance costs.

The Company has a $4.5 billion, five-year credit facility which expires September 28, 2018. The Company also has a commercial paper program under which borrowings are classified as long-term since the program is supported by the $4.5 billion, five-year credit facility. At March 31, 2016, there were $210 million in commercial paper borrowings (gross of debt issuance costs), and there were no outstanding letters of credit issued under the credit facility, resulting in $4,290 million of funds available under this credit facility. Interest under this multicurrency facility is based upon LIBOR, NIBOR or EURIBOR plus 1.125% subject to a ratings-based grid, or the U.S. prime rate. The credit facility contains a financial covenant regarding maximum debt-to-capitalization ratio of 60%. As of March 31, 2016, the Company was in compliance with a debt-to-capitalization ratio of 17.1%.

The Company also had $1,887 million of additional outstanding letters of credit at March 31, 2016 that are under various bilateral 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, 2016 and December 31, 2015, the fair value of the Company’s unsecured Senior Notes approximated $2,463 million and $2,551 million, respectively. At March 31, 2016 and December 31, 2015, the carrying value of the Company’s unsecured Senior Notes approximated $2,976 million and $2,974 million, respectively. The carrying value of the Company’s variable rate borrowings approximates fair value.