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Debt (Senior Notes - Issuances) (Details) - Senior Notes - USD ($)
$ in Millions

12 Months Ended

Aug. 11, 2025

Apr. 09, 2025

Mar. 10, 2025

Dec. 31, 2025

Debt Instrument [Line Items]

Debt Instrument, Face Amount

$ 4,500

MarkWest

Debt Instrument [Line Items]

Interest rate, stated percentage

4.875%

Senior Notes Due April 2035

Debt Instrument [Line Items]

Debt Instrument, Issuance Date

Mar. 10, 2025

Debt Instrument, Face Amount

^[1]

$ 1,000

Interest rate, stated percentage

5.40%

Percent of par

99.398%

Debt Instrument, Maturity Date

Apr. 01, 2035

Repayments of Debt

$ 1,200

Senior Notes Due April 2035 | MPLX LP [Member]

Debt Instrument [Line Items]

Interest rate, stated percentage

5.40%

Debt Instrument, Maturity Date

Apr. 01, 2035

Senior Notes Due April 2055

Debt Instrument [Line Items]

Debt Instrument, Issuance Date

Mar. 10, 2025

Debt Instrument, Face Amount

^[1]

$ 1,000

Interest rate, stated percentage

5.95%

Percent of par

98.331%

Debt Instrument, Maturity Date

Apr. 01, 2055

Senior Notes Due April 2055 | MPLX LP [Member]

Debt Instrument [Line Items]

Interest rate, stated percentage

5.95%

Debt Instrument, Maturity Date

Apr. 01, 2055

Senior Notes Due February 2031

Debt Instrument [Line Items]

Debt Instrument, Issuance Date

Aug. 11, 2025

Debt Instrument, Face Amount

^[2]

$ 1,250

Interest rate, stated percentage

4.80%

Percent of par

99.88%

Debt Instrument, Maturity Date

Feb. 15, 2031

Senior Notes Due February 2031 | MPLX LP [Member]

Debt Instrument [Line Items]

Interest rate, stated percentage

4.80%

Debt Instrument, Maturity Date

Feb. 15, 2031

Senior Notes Due January 2033

Debt Instrument [Line Items]

Debt Instrument, Issuance Date

Aug. 11, 2025

Debt Instrument, Face Amount

^[2]

$ 750

Interest rate, stated percentage

5.00%

Percent of par

98.936%

Debt Instrument, Maturity Date

Jan. 15, 2033

Senior Notes Due January 2033 | MPLX LP [Member]

Debt Instrument [Line Items]

Interest rate, stated percentage

5.00%

Debt Instrument, Maturity Date

Jan. 15, 2033

Senior Notes Due September 2035

Debt Instrument [Line Items]

Debt Instrument, Issuance Date

Aug. 11, 2025

Debt Instrument, Face Amount

^[2]

$ 1,500

Interest rate, stated percentage

5.40%

Percent of par

98.943%

Debt Instrument, Maturity Date

Sep. 15, 2035

Senior Notes Due September 2035 | MPLX LP [Member]

Debt Instrument [Line Items]

Interest rate, stated percentage

5.40%

Debt Instrument, Maturity Date

Sep. 15, 2035

Senior Notes Due September 2055

Debt Instrument [Line Items]

Debt Instrument, Issuance Date

Aug. 11, 2025

Debt Instrument, Face Amount

^[2]

$ 1,000

Interest rate, stated percentage

6.20%

Percent of par

98.277%

Debt Instrument, Maturity Date

Sep. 15, 2055

Senior Notes Due September 2055 | MPLX LP [Member]

Debt Instrument [Line Items]

Interest rate, stated percentage

6.20%

Debt Instrument, Maturity Date

Sep. 15, 2055

Senior Notes Due June 2025 [Member] | MPLX LP [Member]

Debt Instrument [Line Items]

Interest rate, stated percentage

4.875%

4.875%

Debt Instrument, Maturity Date

Jun. 01, 2025

Repayments of Debt

$ 1,189

Senior Notes Due June 2025 [Member] | MarkWest

Debt Instrument [Line Items]

Interest rate, stated percentage

4.875%

Repayments of Debt

$ 11

[1]

On April 9, 2025, MPLX used $1.2 billion of the net proceeds from the issuance of senior notes in March 2025 to redeem all of (i) MPLX’s outstanding $1,189 million aggregate principal amount of 4.875 percent senior notes due June 2025 and (ii) MarkWest’s outstanding $11 million aggregate principal amount of 4.875 percent senior notes due June 2025. The remaining net proceeds from this offering were used for general partnership purposes.

[2]

We used a portion of the net proceeds from this offering to fund the Northwind Midstream Acquisition, including the payment of related fees and expenses, and to increase cash and cash equivalents following the recently completed BANGL Acquisition and BANGL Debt Repayment. The remainder of the net proceeds from this offering were used for general partnership purposes.

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