Debt

A summary of short-term and long-term debt outstanding is as follows:



(in millions)	December 31,
	2017		2016
2.5% Senior Notes, due 2018 ¹	$	399	$	398
3.3% Senior Notes, due 2020 ²	697		696
4.0% Senior Notes, due 2025 ³	692		691
4.4% Senior Notes, due 2026 ⁴	892		891
2.95% Senior Notes, due 2027 ⁵	493		492
6.55% Senior Notes, due 2037 ⁶	396		396
Total debt	3,569		3,564
Less: short-term debt including current maturities	399		—
Long-term debt	$	3,170	$	3,564


¹	Interest payments are due semiannually on February 15 and August 15, and as of December 31, 2017, the unamortized debt discount and issuance costs total $1 million.


²	Interest payments are due semiannually on February 14 and August 14, and as of December 31, 2017, the unamortized debt discount and issuance costs total $3 million.


³	Interest payments are due semiannually on June 15 and December 15, and as of December 31, 2017, the unamortized debt discount and issuance costs total $8 million.


⁴	Interest payments are due semiannually on February 15 and August 15, and as of December 31, 2017, the unamortized debt discount and issuance costs total $8 million.


⁵	Interest payments are due semiannually on January 22 and July 22, and as of December 31, 2017, the unamortized debt discount and issuance costs total $7 million.


⁶	Interest payments are due semiannually on May 15 and November 15, and as of December 31, 2017, the unamortized debt discount and issuance costs total $4 million.

Annual debt maturities are scheduled as follows based on book values as of December 31, 2017: $399 million due in 2018, no amounts due in 2019, $697 million due in 2020, no amounts due in 2021, and $2.5 billion due thereafter.

On September 22, 2016, we issued $500 million of 2.95% senior notes due in 2027. The notes are fully and unconditionally guaranteed by our wholly-owned subsidiary, Standard & Poor's Financial Services LLC. We used the net proceeds to fund the $400 million early repayment of our 5.9% senior notes due in 2017 on October 20, 2016, and intend to use the balance for general corporate purposes.

On August 18, 2015, we issued $2.0 billion of senior notes consisting of $400 million of 2.5% senior notes due in 2018, $700 million of 3.3% senior notes due in 2020 and $900 million of 4.4% senior notes due in 2026. The notes are fully and unconditionally guaranteed by our wholly-owned subsidiary, Standard & Poor's Financial Services LLC. We used the net proceeds to finance the acquisition of SNL.

On May 26, 2015, we issued $700 million of 4.0% senior notes due in 2025 and used a portion of the net proceeds for the repayment of short-term debt, including commercial paper. The 4.0% senior notes will mature on June 15, 2025 and are fully and unconditionally guaranteed by our wholly-owned subsidiary, Standard & Poor's Financial Services LLC.

On June 30, 2017, we entered into a revolving $1.2 billion five-year credit agreement (our "credit facility") that will terminate on June 30, 2022. This credit facility replaced our $1.2 billion five-year credit facility that was scheduled to terminate on June 30, 2020. The previous credit facility was canceled immediately after the new credit facility became effective. There were no outstanding borrowings under the previous credit facility when it was replaced.

We have the ability to borrow a total of $1.2 billion through our commercial paper program, which is supported by our credit facility. There were no commercial paper borrowings outstanding as of December 31, 2017 and 2016.

Depending on our corporate credit rating, we pay a commitment fee of 8 to 17.5 basis points for our credit facility, whether or not amounts have been borrowed. We currently pay a commitment fee of 12.5 basis points. The interest rate on borrowings under our credit facility is, at our option, calculated using rates that are primarily based on either the prevailing London Inter-Bank Offer Rate, the prime rate determined by the administrative agent or the Federal Funds Rate. For certain borrowings under this credit facility, there is also a spread based on our corporate credit rating.

Our credit facility contains certain covenants. The only financial covenant requires that our indebtedness to cash flow ratio, as defined in our credit facility, is not greater than 4 to 1, and this covenant level has never been exceeded.