NOTES PAYABLE AND LONG-TERM DEBT

As of December 31, 2014 and 2013, the Company had short-term and long-term debt outstanding as follows:



	December 31,
(millions of dollars)	2014		2013
Short-term debt
Short-term borrowings	$	601.2	$	84.8
Receivables securitization	—		110.0
Total short-term debt	$	601.2	$	194.8

Long-term debt
5.75% Senior notes due 11/01/16 ($150 million par value)	$	149.8	$	149.7
8.00% Senior notes due 10/01/19 ($134 million par value)	134.0		133.9
4.625% Senior notes due 09/15/20 ($250 million par value)	248.4		248.2
7.125% Senior notes due 02/15/29 ($121 million par value)	119.4		119.4
Multi-currency revolving credit facility	—		320.0
Term loan facilities and other	75.1		40.4
Unamortized portion of debt derivatives	12.1		16.2
Total long-term debt	$	738.8	$	1,027.8
Less: current portion	22.5		6.8
Long-term debt, net of current portion	$	716.3	$	1,021.0

The weighted average interest rate on short-term borrowings outstanding as of December 31, 2014 and 2013 was 0.8% and 1.5%, respectively. The weighted average interest rate on all borrowings outstanding as of December 31, 2014 and 2013 was 2.9% and 3.7%, respectively.

Annual principal payments required as of December 31, 2014 are as follows :



(millions of dollars)
2015	$	623.7
2016	165.4
2017	33.6
2018	1.2
2019	135.2
After 2019	384.0
Total payments	$	1,343.1
Less: unamortized discounts	3.1
Total	$	1,340.0

The Company's long-term debt includes various financial covenants, none of which are expected to restrict future operations.

On June 30, 2014, the Company amended and extended its $750 million multi-currency revolving credit facility (which included a feature that allowed the Company's borrowings to be increased to $1 billion) to 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 December 31, 2014 and expects to remain compliant in future periods. At December 31, 2014, the Company had no outstanding borrowings under this facility. At December 31, 2013, the Company had outstanding borrowings of $320.0 million under the multi-currency revolving credit agreement.

On March 12, 2014, the Company entered into a new commercial paper program pursuant to which the Company may 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. At December 31, 2014, the Company had outstanding borrowings of $460.9 million under this program, which is classified in the Consolidated Balance Sheet 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.

On February 11, 2014, the Company's universal shelf registration expired. The Company filed a new universal shelf registration with the Securities and Exchange Commission on February 28, 2014.

On April 9, 2009, the Company issued $373.8 million in convertible senior notes, which were settled in April 2012 by delivering approximately 22.8 million shares of common stock held in treasury to the note holders. The settlement resulted in a reduction in the current portion of long-term debt of $373.8 million, a reduction in common stock held in treasury of $617.3 million and a reduction in capital in excess of par value of $243.5 million. Prior to the settlement, the Company accreted the discounted carrying value of the convertible notes to their face value over the term of the notes.

The total interest expense related to the convertible senior notes in the Company’s Consolidated Statements of Operations for the years ended December 31, 2014, 2013 and 2012 was as follows:



	Year Ended December 31,
(millions of dollars)	2014		2013		2012
Interest expense	$	—	$	—	$	9.0
Non-cash portion	—		—		5.3

In conjunction with the convertible senior note offering, the Company entered into a bond hedge overlay, including both call options and warrants, at a net pre-tax cost of $25.2 million, effectively raising the conversion premium to 50%, or approximately $19.31 per share. On April 16, 2012, the Company settled the call option portion of the bond hedge overlay, receiving approximately 13.0 million shares of its common stock. The settlement resulted in an increase to common stock held in treasury of $503.9 million offset by an increase to capital in excess of par value of $503.9 million.

During the third and fourth quarters of 2012, the Company settled the warrants included in the bond hedge overlay, delivering approximately 9.8 million shares of its common stock held in treasury, resulting in a decrease to common stock held in treasury of $338.5 million offset by a decrease to capital in excess of par value of $338.5 million.

As of December 31, 2014 and 2013, the estimated fair values of the Company's senior unsecured notes totaled $750.3 million and $729.7 million, respectively. The estimated fair values were $98.7 million and $78.5 million higher than their carrying value at December 31, 2014 and 2013, 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 $28.3 million and $27.8 million at December 31, 2014 and 2013, respectively. The letters of credit typically act as guarantees of payment to certain third parties in accordance with specified terms and conditions.