Note 10: Long-Term Debt

As of December 31, 2015 and 2014, our debt had an estimated fair value of $58.0 billion and $55.3 billion, respectively. The estimated fair value of our publicly traded debt is primarily based on Level 1 inputs that use quoted market values for the debt. The estimated fair value of debt for which there are no quoted market prices is based on Level 2 inputs that use interest rates available to us for debt with similar terms and remaining maturities. See Note 20 for additional information on our cross-guarantee structure.

Debt Instruments

Revolving Credit Facilities

As of December 31, 2015, Comcast and Comcast Cable Communications, LLC had a $6.25 billion revolving credit facility due June 2017 with a syndicate of banks (“Comcast revolving credit facility”). The interest rate on this facility consists of a base rate plus a borrowing margin that is determined based on our credit rating. As of December 31, 2015, the borrowing margin for London Interbank Offered Rate (“LIBOR”) based borrowings was 1.00%. This revolving credit facility requires that we maintain certain financial ratios based on our debt and our operating income before depreciation and amortization, as defined in the credit facility. We were in compliance with all financial covenants for all periods presented.

As of December 31, 2015, NBCUniversal Enterprise had a $1.35 billion revolving credit facility due March 2018 with a syndicate of banks (“NBCUniversal Enterprise revolving credit facility”). The interest rate on this facility consists of a base rate plus a borrowing margin that is determined based on our credit rating. As of December 31, 2015, the borrowing margin for LIBOR-based borrowings was 1.00%.

As of December 31, 2015, amounts available under our consolidated credit facilities, net of amounts outstanding under our commercial paper programs and outstanding letters of credit, totaled $6.4 billion, which included $775 million available under the NBCUniversal Enterprise revolving credit facility.

Term Loans

As a result of the Universal Studios Japan transaction, we consolidated ¥400 billion of term loans having a final maturity of November 2020. In accordance with acquisition accounting, these debt securities were recorded at fair value as of the acquisition date. These term loans contain financial and operating covenants and are secured by the assets of Universal Studios Japan and the equity interests of the investors. We do not guarantee these term loans and they are otherwise nonrecourse to us.

Commercial Paper Programs

Our commercial paper programs provide a lower-cost source of borrowing to fund our short-term working capital requirements. The maximum borrowing capacity under the Comcast commercial paper program is $6.25 billion and it is supported by the Comcast revolving credit facility. The maximum borrowing capacity under the NBCUniversal Enterprise commercial paper program is $1.35 billion and it is supported by the NBCUniversal Enterprise revolving credit facility.

Letters of Credit

As of December 31, 2015, we and certain of our subsidiaries had unused irrevocable standby letters of credit totaling $464 million to cover potential fundings under various agreements.

Note 10: Long-Term Debt

As of December 31, 2015 and 2014, our debt, excluding the note payable to Comcast, had an estimated fair value of $13.4 billion and $11.5 billion, respectively. The estimated fair value of our publicly traded debt is primarily based on Level 1 inputs that use quoted market values for the debt. The estimated fair value of debt for which there are no quoted market prices is based on Level 2 inputs that use interest rates available to us for debt with similar terms and remaining maturities.

Term Loans

As a result of the Universal Studios Japan transaction, we consolidated ¥400 billion of term loans having a final maturity of November 2020. In accordance with acquisition accounting, these debt securities were recorded at fair value as of the acquisition date. These term loans contain financial and operating covenants and are secured by the assets of Universal Studios Japan and the equity interests of the investors. We do not guarantee these term loans and they are otherwise nonrecourse to us.

Debt Repayments

In April 2015, we repaid at maturity $1 billion aggregate principal amount of 3.65% senior notes due 2015.

Cross-Guarantee Structure

We, Comcast and a 100% owned cable holding company subsidiary of Comcast (“CCCL Parent”) fully and unconditionally guarantee each other’s debt securities. As of December 31, 2015, we guaranteed $35.1 billion of outstanding debt securities of Comcast and CCCL Parent. We also fully and unconditionally guarantee the Comcast revolving credit facility, of which no amounts were outstanding as of December 31, 2015.

We do not, however, guarantee the obligations of NBCUniversal Enterprise with respect to its $4 billion aggregate principal amount of senior notes, $1.35 billion revolving credit facility and associated commercial paper program, or $725 million liquidation preference of Series A cumulative preferred stock.