Accumulated Other Comprehensive Income Accumulated Other Comprehensive Income

12 Months Ended

Dec. 31, 2019

Accumulated Other Comprehensive Income (Loss) [Line Items]

Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]

Accumulated Other Comprehensive Loss

MPLX records an accumulated other comprehensive loss on the Consolidated Balance Sheets relating to pension and other post-retirement benefits provided by LOOP and Explorer to their employees. MPLX is not a sponsor of these benefit plans. As a transfer between entities under common control, MPLX recorded the Joint-Interest Acquisition from MPC on the Consolidated Balance Sheets at MPC’s historical basis, which included accumulated other comprehensive loss. MPLX’s assumption of the accumulated other comprehensive loss balance had no effect on MPLX’s comprehensive income during the period as the balance was accumulated while under the ownership of MPC.

The following table shows the changes in “Accumulated other comprehensive loss” by component during the period December 31, 2017 through December 31, 2019:

(In millions)	Pension Benefits			Other Post-Retirement Benefits			Total
Balance at December 31, 2017(1)	$	(13	)	$	(1	)	$	(14	)
Other comprehensive loss - remeasurements(2)	(1		)	(1		)	(2		)
Balance at December 31, 2018(1)	(14		)	(2		)	(16		)
Other comprehensive income - remeasurements(2)	—			1			1
Balance as of December 31, 2019(1)	$	(14	)	$	(1	)	$	(15	)

(1) These components of “Accumulated other comprehensive loss” are included in the computation of net periodic benefit cost by LOOP and Explorer and are therefore included on the Consolidated Statements of Income under the caption “Income/(loss) from equity method investments.”

(2)

Components of other comprehensive loss - remeasurements relate to actuarial gains and losses as well as amortization of prior service costs. MPLX records an adjustment to “Comprehensive income” in accordance with its ownership interest in LOOP and Explorer.