Debt consisted of the following (in millions):



	March 31, 2019		December 31, 2018
SHORT-TERM DEBT
Other	$	149	$	66
Total short-term debt	149		66

LONG-TERM DEBT
Senior notes, net of unamortized discounts and debt issuance costs of $57 and $59, respectively ^{(1) (2)}	8,943		8,941
GO Zone term loans, net of debt issuance costs of $2 and $2, respectively, bearing a weighted-average interest rate of 3.2% and 3.1%, respectively ⁽²⁾	198		198
Other	36		4
Total long-term debt	9,177		9,143
Total debt	$	9,326	$	9,209


⁽¹⁾	As of March 31, 2019, we classified our $500 million, 5.75% senior notes due January 2020 and our $500 million, 2.60% senior notes due December 2019 as long-term, and as of December 31, 2018, we classified our $500 million, 2.60% senior notes due December 2019 as long-term based on our ability and intent to refinance such amounts on a long-term basis.

⁽²⁾

Our fixed-rate senior notes had a face value of approximately $9.0 billion at both March 31, 2019 and December 31, 2018. We estimated the aggregate fair value of these notes as of March 31, 2019 and December 31, 2018 to be approximately $9.1 billion and $8.6 billion, respectively. Our fixed-rate senior notes are traded among institutions, and these trades are routinely published by a reporting service. Our determination of fair value is based on reported trading activity near the end of the reporting period. We estimate that the carrying value of outstanding borrowings under our GO Zone term loans approximates fair value as interest rates reflect current market rates. The fair value estimates for our senior notes and GO Zone term loans are based upon observable market data and are classified in Level 2 of the fair value hierarchy.