Debt

The Partnership’s outstanding borrowings consisted of the following:



(In millions)	March 31, 2018			December 31, 2017
MPLX LP:
Bank revolving credit facility due 2022	$	—		$	505
5.500% senior notes due February 2023	710			710
3.375% senior notes due March 2023	500			—
4.500% senior notes due July 2023	989			989
4.875% senior notes due December 2024	1,149			1,149
4.000% senior notes due February 2025	500			500
4.875% senior notes due June 2025	1,189			1,189
4.125% senior notes due March 2027	1,250			1,250
4.000% senior notes due March 2028	1,250			—
4.500% senior notes due April 2038	1,750			—
5.200% senior notes due March 2047	1,000			1,000
4.700% senior notes due April 2048	1,500			—
4.900% senior notes due April 2058	500			—
Consolidated subsidiaries:
MarkWest - 4.500% - 5.500% senior notes, due 2023-2025	63			63
MPL - capital lease obligations due 2020	7			7
Total	12,357			7,362
Unamortized debt issuance costs	(79		)	(27		)
Unamortized discount	(416		)	(389		)
Amounts due within one year	(1		)	(1		)
Total long-term debt due after one year	$	11,861		$	6,945

Credit Agreements

On July 21, 2017, the Partnership entered into a syndicated credit agreement to replace its previously outstanding $2.0 billion five-year bank revolving credit facility with a $2.25 billion five-year bank revolving credit facility that expires in July 2022 (the “MPLX Credit Agreement”). The financial covenants and the interest rate terms contained in the new credit agreement are substantially the same as those contained in the previous bank revolving credit facility. During the three months ended March 31, 2018, the Partnership borrowed $50 million under the MPLX Credit Agreement, at an average interest rate of 2.975 percent and repaid $555 million. At March 31, 2018, the Partnership had no outstanding borrowings and $3 million letters of credit outstanding under the new facility, resulting in total availability of $2.247 billion, or 99.9 percent of the borrowing capacity.

On January 2, 2018, the Partnership entered into a term loan agreement with a syndicate of lenders providing for a $4.1 billion, 364-day term loan facility. The Partnership drew the entire amount of the term loan facility in a single borrowing on February 1, 2018 with the entire amount then being repaid on February 8, 2018 as described below. The proceeds from the term loan facility were used to fund the cash portion of the dropdown consideration.

Senior Notes

On February 8, 2018, the Partnership issued $5.5 billion of senior notes in a public offering, consisting of $500 million aggregate principal amount of 3.375 percent unsecured senior notes due March 2023, $1.25 billion aggregate principal amount of 4.0 percent unsecured senior notes due March 2028, $1.75 billion aggregate principal amount of 4.5 percent unsecured senior notes due April 2038, $1.5 billion aggregate principal amount of 4.7 percent unsecured senior notes due April 2048, and $500 million aggregate principal amount of 4.9 percent unsecured senior notes due April 2058 (collectively, the “2018 New Senior Notes”). The notes were offered at a price to the public of 99.931 percent, 99.551 percent, 98.811 percent, 99.348 percent, and 99.289 percent of par, respectively. Also on February 8, 2018, $4.1 billion of the net proceeds were used to repay the 364-day term loan facility, which was drawn on February 1, 2018 to fund the cash portion of the dropdown consideration. The remaining proceeds were used to repay outstanding borrowings under the MPLX Credit Agreement and the intercompany loan agreement with MPC Investment, as well as for general partnership purposes.

On February 10, 2017, the Partnership completed a public offering of $2.25 billion aggregate principal amount of unsecured senior notes, consisting of (i) $1.25 billion aggregate principal amount of 4.125 percent senior notes due in March 2027 and (ii) $1.0 billion aggregate principal amount of 5.200 percent senior notes due in March 2047 (collectively, the “2017 New Senior Notes”). The net proceeds from the New Senior Notes totaled approximately $2.22 billion, after deducting underwriting discounts, and were used for general partnership purposes and capital expenditures. Interest on each series of the notes is payable semi-annually in arrears on March 1 and September 1, commencing on September 1, 2017.