Notes Payable and Long-Term Debt

As of September 30, 2015 and December 31, 2014, the Company had short-term and long-term debt outstanding as follows:



	September 30,		December 31,
(in millions)	2015		2014
Short-term debt
Short-term borrowings	$	66.6	$	601.2

Long-term debt
5.75% Senior notes due 11/01/16 ($150 million par value)	$	149.9	$	149.8
8.00% Senior notes due 10/01/19 ($134 million par value)	134.0		134.0
4.625% Senior notes due 09/15/20 ($250 million par value)	248.6		248.4
3.375% Senior notes due 03/15/25 ($500 million par value)	499.0		—
7.125% Senior notes due 02/15/29 ($121 million par value)	119.5		119.4
4.375% Senior notes due 03/15/45 ($500 million par value)	498.4		—
Term loan facilities and other	81.3		75.1
Unamortized portion of debt derivatives	11.8		12.1
Total long-term debt	1,742.5		738.8
Less: current portion	8.0		22.5
Long-term debt, net of current portion	$	1,734.5	$	716.3

The weighted average interest rate on short-term borrowings outstanding as of September 30, 2015 and December 31, 2014 was 2.0% and 0.8%, respectively. The weighted average interest rate on all borrowings outstanding as of September 30, 2015 and December 31, 2014 was 4.6% and 2.9%, respectively.

On March 16, 2015, BorgWarner Inc. issued $500 million in 3.375% senior notes due March 2025 and $500 million in 4.375% senior notes due March 2045. Interest is payable semi-annually in arrears on March 15 and September 15 of each year.

The Company has a $1 billion multi-currency revolving credit facility which includes a feature that allows the Company's borrowings to be increased to $1.25 billion. The facility provides for borrowings through June 30, 2019. The Company has one key financial covenant as part of the credit agreement which is a debt to EBITDA ("Earnings Before Interest, Taxes, Depreciation and Amortization") ratio. The Company was in compliance with the financial covenant at September 30, 2015 and expects to remain compliant in future periods. At September 30, 2015 and December 31, 2014, the Company had no outstanding borrowings under this facility.

The Company's commercial paper program allows the Company to issue short-term, unsecured commercial paper notes up to a maximum aggregate principal amount outstanding of $1 billion. Under this program, the Company may issue notes from time to time and will use the proceeds for general corporate purposes. The Company had no borrowings outstanding under this program at September 30, 2015. At December 31, 2014, the Company had outstanding borrowings of $460.9 million under this program, which is classified in the Condensed Consolidated Balance Sheets in Notes payable and other short-term debt.

The total current combined borrowing capacity under the multi-currency revolving credit facility and commercial paper program cannot exceed $1 billion.

As of September 30, 2015 and December 31, 2014, the estimated fair values of the Company’s senior unsecured notes totaled $1,697.9 million and $750.3 million, respectively. The estimated fair values were $48.5 million and $98.7 million higher than their carrying value at September 30, 2015 and December 31, 2014, respectively. Fair market values of the senior unsecured notes are developed using observable values for similar debt instruments, which are considered Level 2 inputs as defined by ASC Topic 820. The carrying values of the Company's multi-currency revolving credit facility and commercial paper program approximates fair value. The fair value estimates do not necessarily reflect the values the Company could realize in the current markets.

The Company had outstanding letters of credit of $32.9 million and $28.3 million at September 30, 2015 and December 31, 2014, respectively. The letters of credit typically act as guarantees of payment to certain third parties in accordance with specified terms and conditions.