11. Debt

Senior Notes: Summarized below are the carrying values of our senior notes at March 31, 2013 and December 31, 2012:

	March 31, 2013		December 31, 2012
2.450% senior notes due 2015	$	518.4	$	520.1
1.900% senior notes due 2017	501.1		500.6
3.950% senior notes due 2020	501.5		499.0
3.250% senior notes due 2022	993.6		1,002.1
5.700% senior notes due 2040	249.5		249.5
Total long-term debt	$	2,764.1	$	2,771.3

At March 31, 2013, the fair value of our outstanding Senior Notes was $2.868 billion and represented a Level 2 measurement within the fair value measurement hierarchy.

During the year ended December 31, 2012, we entered into treasury rate locks in anticipation of issuing the fixed-rate notes that were issued in August 2012. As of March 2013, a balance of $33.1 million in losses remained in OCI related to treasury rate locks and will be recognized as interest expense over the life of the 2017 notes and the 2022 notes.

At March 31, 2013, we were party to pay-floating, receive-fixed interest rate swap contracts designated as fair value hedges of fixed-rate notes as described in Note 7. Our swap contracts outstanding at March 31, 2013 effectively convert the hedged portion of our fixed-rate notes to floating rates. From time to time we terminate the hedging relationship on certain of our swap contracts by settling the contracts or by entering into offsetting contracts. Any net proceeds received or paid in these settlements are accounted for as a reduction or increase of current and future interest expense associated with the previously hedged notes. As of March 31, 2013, we had a balance of $26.0 million of gains recorded as a reduction of our debt as a result of past swap contract settlements, including $2.5 million related to the settlement of $400.0 million of swap contracts during the three months ended March 31, 2013 that had previously been designated as a hedge of our 3.950% senior notes due 2020. In April 2013, an additional $800.0 million in swap contracts were settled with combined gains of $3.8 million accounted for as a reduction of future interest expense associated with these notes.

Commercial Paper: The carrying value of Commercial Paper as of March 31, 2013 and December 31, 2012 was $362.0 million and $308.5 million, respectively, and approximated its fair value. The effective interest rate on the outstanding Commercial Paper balance at March 31, 2013 was 0.4%.

Senior Unsecured Credit Facility: We maintain a senior unsecured revolving credit facility (Credit Facility) that provides revolving credit in the aggregate amount of $1.000 billion, which was increased to $1.500 billion in April 2013. The term of the Credit Facility was also extended from September 2, 2016 to April 18, 2018. Subject to certain conditions, we have the right to increase the amount of the Credit Facility (but in no event more than one time per annum), up to a maximum aggregate amount of $1.750 billion. Amounts may be borrowed in U.S. dollars for working capital, capital expenditures and other corporate purposes. The Credit Facility serves as backup liquidity for our Commercial Paper borrowings. At March 31, 2013 and December 31, 2012, there was no outstanding borrowing against the Credit Facility.

The Credit Facility contains affirmative and negative covenants including certain customary financial covenants. We were in compliance with all financial covenants as of March 31, 2013.