Debt

Our total debt, including short-term and long-term debt, consisted of the following as of September 30, 2018 and December 31, 2017 (in millions):



	As of September 30, 2018		As of December 31, 2017
Debt:
Short-term debt:
Commercial Paper	$	1,198	$	1,233
2018 Senior Notes (2.50% senior unsecured notes due October 15, 2018)	—		600
Total short-term debt	1,198		1,833
Long-term debt:
2020 Senior Notes (2.75% senior unsecured notes due December 1, 2020)	1,245		1,244
2022 Senior Notes (2.35% senior unsecured notes due September 15, 2022)	496		495
2023 Senior Notes (3.45% senior unsecured notes due September 21, 2023)	397		—
2023 Senior Notes (4.00% senior unsecured notes due October 15, 2023)	793		791
2025 Senior Notes (3.75% senior unsecured notes due December 1, 2025)	1,243		1,242
2027 Senior Notes (3.10% senior unsecured notes due September 15, 2027)	495		495
2028 Senior Notes (3.75% senior unsecured notes due September 21, 2028)	591		—
2048 Senior Notes (4.25% senior unsecured notes due September 21, 2048)	1,228		—
Total long-term debt	6,488		4,267
Total debt	$	7,686	$	6,100

Amended Credit Facility

We have a $3.4 billion senior unsecured revolving credit facility, or the Credit Facility, pursuant to a credit agreement with Wells Fargo Bank, N.A., as primary administrative agent, issuing lender and swing-line lender, Bank of America, N.A., as syndication agent, backup administrative agent and swing-line lender, and the lenders party thereto. On August 9, 2018, we agreed with the lenders to extend the final maturity date of the Credit Facility from August 18, 2022 to August 9, 2023 and make certain other changes, herein referred to as the Amended Credit Facility. We incurred debt issuance costs of $2 million relating to the Amended Credit Facility and these costs are included in the accompanying consolidated balance sheet as other non-current assets and will be amortized over the life of the Amended Credit Facility.

The Amended Credit Facility includes an option for us to propose an increase in the aggregate amount available for borrowing by up to $975 million, subject to the consent of the lenders funding the increase, and certain other conditions. No amounts were outstanding under the Amended Credit Facility as of September 30, 2018. As of September 30, 2018, of the $3.4 billion that is currently available for borrowing under the Amended Credit Facility, $1.2 billion is required to back-stop the amount outstanding under our Commercial Paper Program and $105 million is required to support certain broker-dealer subsidiary commitments.

The amount required to back-stop the amounts outstanding under the Commercial Paper Program will fluctuate as we increase or decrease our commercial paper borrowings. The remaining $2.1 billion available under the Amended Credit Facility as of September 30, 2018 is available for us to use for working capital and general corporate purposes including, but not limited to, acting as a back-stop to future increases in the amounts outstanding under the Commercial Paper Program.

Commercial Paper Program

We have entered into a U.S. dollar commercial paper program, or the Commercial Paper Program. Our Commercial Paper Program is currently backed by the borrowing capacity available under the Amended Credit Facility, equal to the amount of the commercial paper that is issued and outstanding at any given point in time. The effective interest rate of commercial paper issuances does not materially differ from short-term interest rates (such as USD LIBOR). The fluctuation of these rates due to market conditions may impact our interest expense. During the nine months ended September 30, 2018, we repaid a net amount of $35 million of outstanding Commercial Paper.

Commercial paper notes of $1.2 billion with original maturities ranging from one to 81 days were outstanding as of September 30, 2018 under our Commercial Paper Program. As of September 30, 2018, the weighted average interest rate on the $1.2 billion outstanding under our Commercial Paper Program was 2.15% per annum, with a weighted average maturity of 23 days.

Senior Notes

On August 13, 2018, we issued $2.25 billion in new aggregate senior notes. The senior notes comprise $400 million in aggregate principal amount of 3.45% senior notes due in 2023, or the 2023 Senior Notes, $600 million in aggregate principal amount of 3.75% senior notes due in 2028, or the 2028 Senior Notes, and $1.25 billion in aggregate principal amount of 4.25% senior notes due in 2048, or the 2048 Senior Notes, and together with the 2023 Senior Notes and the 2028 Senior Notes, the Newly-Issued Senior Notes. We used the net proceeds from the offering of the Newly-Issued Senior Notes for general corporate purposes, including to fund the redemption of the $600 million aggregate principal amount of 2.50% Senior Notes due October 2018 and to refinance all of our issuances under our Commercial Paper Program that resulted from acquisitions and investments in the last nine months.

We incurred debt issuance costs of $21 million relating to the issuance of the Newly-Issued Senior Notes and they are presented in the accompanying consolidated balance sheet as a deduction from the carrying amount of the related debt liability and will be amortized over their respective lives. The Newly-Issued Senior Notes contain affirmative and negative covenants, including, but not limited to, certain redemption rights, limitations on liens and indebtedness and limitations on certain mergers, sales, dispositions and lease-back transactions.