	As of December 31,
	2018			2017
Current portion of long-term debt
2.000% Senior Notes due 2018	$	-		$	1,150.0
4.625% Senior Notes due 2019		500.0			-
U.S. Term Loan B		25.0			75.0
Total short-term debt	$	525.0		$	1,225.0
Long-term debt
4.625% Senior Notes due 2019	$	-		$	500.0
2.700% Senior Notes due 2020		1,500.0			1,500.0
Floating Rate Notes due 2021		450.0			-
3.375% Senior Notes due 2021		300.0			300.0
3.150% Senior Notes due 2022		750.0			750.0
3.700% Senior Notes due 2023		300.0			-
3.550% Senior Notes due 2025		2,000.0			2,000.0
4.250% Senior Notes due 2035		253.4			253.4
5.750% Senior Notes due 2039		317.8			317.8
4.450% Senior Notes due 2045		395.4			395.4
1.414% Euro Notes due 2022		571.6			600.4
2.425% Euro Notes due 2026		571.6			600.4
U.S. Term Loan A		-			835.0
U.S. Term Loan B		200.0			600.0
U.S. Term Loan C		535.0			-
Japan Term Loan A		105.3			103.2
Japan Term Loan B		191.7			187.9
Other long-term debt		-			4.1
Debt discount and issuance costs		(42.7	)		(53.2	)
Adjustment related to interest rate swaps		14.6			23.1
Total long-term debt	$	8,413.7		$	8,917.5

At December 31, 2018, our total debt balance consisted of $7.9 billion aggregate principal amount of senior notes, which included $1.1 billion of Euro-denominated senior notes (“Euro notes”), $225.0 million outstanding under a U.S. term loan (“U.S. Term Loan B”) that will mature on September 30, 2019, $535.0 million outstanding under a U.S. term loan (“U.S. Term Loan C”) that will mature on December 14, 2020, an 11.7 billion Japanese Yen term loan agreement (“Japan Term Loan A”) and a 21.3 billion Japanese Yen term loan agreement (“Japan Term Loan B”) that each will mature on September 27, 2022, and other debt and fair value adjustments totaling $14.6 million, partially offset by debt discount and issuance costs of $42.7 million.

On December 14, 2018, we entered into a credit agreement (the “2018 Credit Agreement”) that provides for U.S. Term Loan C, which is a two-year unsecured multi-draw term loan facility for the Company in the principal amount of $900.0 million, with a maturity date of December 14, 2020. On December 14, 2018, we borrowed $675.0 million under U.S. Term Loan C and utilized those borrowings: (i) to repay the full $295.0 million balance of a U.S. term loan (“U.S. Term Loan A”), (ii) to repay $375.0 million of the $600.0 million balance of U.S. Term Loan B; and (iii) for general corporate purposes and transaction costs. In January 2019, we borrowed an additional $200.0 million under U.S. Term Loan C and used those proceeds, along with cash on hand, to repay the remaining $225.0 million outstanding under U.S. Term Loan B. Under the applicable accounting rules, since $200.0 million of U.S. Term Loan B was refinanced on a long-term basis before the issuance of these consolidated financial statements, we classified the refinanced portion of U.S. Term Loan B as long-term as of December 31, 2018.

On March 19, 2018, we completed the offering of $450.0 million aggregate principal amount of our floating rate senior notes due March 19, 2021 and $300.0 million aggregate principal amount of our 3.700% senior notes due March 19, 2023. Interest on the floating rate senior notes is equal to three-month LIBOR plus 0.750% and is payable quarterly, commencing on June 19, 2018, until maturity. Interest is payable on the 3.700% senior notes semi-annually, commencing on September 19, 2018, until maturity. We received net proceeds of $749.5 million from this offering. On April 2, 2018, these proceeds, together with borrowings under the Multicurrency Revolving Facility (as defined below) and cash on hand, were used to repay the 2.000% Senior Notes due 2018.

On September 22, 2017, we entered into a term loan agreement for the Japan Term Loan B, and an amended and restated term loan agreement, which amended and restated the Japan Term Loan A loan agreement dated as of May 24, 2012, as amended as of October 31, 2014. As described above, the term loans under both of these agreements will mature on September 27, 2022. Each of these term loans bears interest at a fixed rate of 0.635 percent per annum.

On December 13, 2016, we completed the offering of €500 million aggregate principal amount of our 1.414% Euro notes due December 13, 2022 and €500 million aggregate principal amount of our 2.425% Euro notes due December 13, 2026. Interest is payable on each series of Euro notes on December 13 of each year until maturity.

In 2016, we also entered into U.S. Term Loan B and borrowed $750.0 million thereunder to repay outstanding borrowings under a previous multicurrency revolving facility incurred in connection with the acquisition of LDR.

In 2016, we used a portion of the funds received from the above-described note issuances and borrowings to repay other outstanding debt. The repayments resulted in debt extinguishment charges of $53.3 million recorded as part of other expense, net.

We have a revolving credit and term loan agreement (the “2016 Credit Agreement”) and a first amendment to our credit agreement executed in 2014 (the “2014 Credit Agreement”). The 2016 Credit Agreement contains the U.S. Term Loan B and a five-year unsecured multicurrency revolving facility of $1.5 billion (the “Multicurrency Revolving Facility”). The Multicurrency Revolving Facility replaced the previous multicurrency revolving facility under the 2014 Credit Agreement and will mature on September 30, 2021, with two available one-year extensions at our discretion. The 2014 Credit Agreement provided for U.S. Term Loan A, which was repaid in full with borrowings under U.S. Term Loan C in December 2018.

Borrowings under the 2018 Credit Agreement bear interest at floating rates based upon, for Eurodollar-indexed loans, LIBOR for the applicable interest period plus a margin of 0.875% per annum, or for non-Eurodollar-indexed loans, an alternate base rate plus a margin of 0.0%. Under the terms of U.S. Term Loan C, the remaining balance is due on the maturity date of December 14, 2020. We have paid $140.0 million in principal under U.S. Term Loan C, resulting in $535.0 million outstanding on the U.S. Term Loan C as of December 31, 2018. The interest rate at December 31, 2018 was 3.4 percent on U.S. Term Loan C. We borrowed an additional $200.0 million under U.S. Term Loan C in January 2019.

Borrowings under the 2014 and 2016 Credit Agreements generally bear interest at floating rates based upon indices determined by the currency of the borrowing, or at an alternate base rate, in each case, plus an applicable margin determined by reference to our senior unsecured long-term credit rating, or, in the case of borrowings under the Multicurrency Revolving Facility only, at a fixed rate determined through a competitive bid process. We pay a facility fee on the aggregate amount of the Multicurrency Revolving Facility at a rate determined by reference to our senior unsecured long-term credit rating.

The 2018 Credit Agreement, the 2016 Credit Agreement and the 2014 Credit Agreement, as amended, contain customary affirmative and negative covenants and events of default for unsecured financing arrangements, including, among other things, limitations on consolidations, mergers and sales of assets. Financial covenants under the 2018, 2016 and 2014 Credit Agreements include a consolidated indebtedness to consolidated EBITDA ratio of no greater than 5.0 to 1.0 through June 30, 2017, and no greater than 4.5 to 1.0 thereafter. If our credit rating falls below investment grade, additional restrictions would result, including restrictions on investments and payment of dividends. We were in compliance with all covenants under the 2018, 2016 and 2014 Credit Agreements as of December 31, 2018. As of December 31, 2018, there were no borrowings outstanding under the Multicurrency Revolving Facility.

We may, at our option, redeem our senior notes, in whole or in part, at any time upon payment of the principal, any applicable make-whole premium, and accrued and unpaid interest to the date of redemption, except that the Floating Rate Notes due 2021 may not be redeemed until on or after March 20, 2019 and such notes do not have any applicable make-whole premium. In addition, we may redeem, at our option, the 2.700% Senior Notes due 2020, the 3.375% Senior Notes due 2021, the 3.150% Senior Notes due 2022, the 3.700% Senior Notes due 2023, the 3.550% Senior Notes due 2025, the 4.250% Senior Notes due 2035 and the 4.450% Senior Notes due 2045 without any make-whole premium at specified dates ranging from one month to six months in advance of the scheduled maturity date.

The estimated fair value of our senior notes as of December 31, 2018, based on quoted prices for the specific securities from transactions in over-the-counter markets (Level 2), was $7,798.9 million. The estimated fair value of Japan Term Loan A and Japan Term Loan B, in the aggregate, as of December 31, 2018, based upon publicly available market yield curves and the terms of the debt (Level 2), was $294.7 million. The carrying values of U.S. Term Loan B and U.S. Term Loan C approximate fair value as they bear interest at short-term variable market rates.

We entered into interest rate swap agreements which we designated as fair value hedges of underlying fixed-rate obligations on our senior notes due 2019 and 2021. These fair value hedges were settled in 2016. In 2016, we entered into various variable-to-fixed interest rate swap agreements that were accounted for as cash flow hedges of U.S. Term Loan B. In 2018, we entered into cross-currency interest rate swaps that we designated as net investment hedges. The excluded component of these net investment hedges is recorded in interest expense, net. See Note 13 for additional information regarding our interest rate swap agreements.

At December 31, 2018 and 2017, the weighted average interest rate for our borrowings was 3.1 percent and 2.9 percent, respectively. We paid $282.8 million, $317.5 million, and $363.1 million in interest during 2018, 2017, and 2016, respectively.