Benefit Plans (Tables)

9 Months Ended

Sep. 30, 2020

Retirement Benefits [Abstract]

Schedule of Net Periodic Benefit (Income) Cost

Net periodic benefit (income) cost consisted of the following: 

	For the Nine Months Ended September 30,								For the Three Months Ended September 30,
	Pension				Postretirement				Pension				Postretirement
	2020		2019		2020		2019		2020		2019		2020		2019
	(in millions)
Service cost	$	55	$	52	$	13	$	12	$	18	$	17	$	5	$	4
Interest cost	188		229		44		57		62		77		14		17
Expected return on plan assets	(376)		(431)		(11)		(11)		(125)		(143)		(4)		(4)
Amortization:
Net loss	108		119		7		3		55		39		—		(3)
Prior service cost (credit)	4		4		(22)		(22)		2		1		(7)		(8)
Curtailment	—		7		—		5		—		—		—		—
Net periodic benefit (income) cost	$	(21)	$	(20)	$	31	$	44	$	12	$	(9)	$	8	$	6