Retirement Benefits - Reconciliation of Level 3 Assets and Liabilities measured at Fair Value for Pension and Other Postretirement Benefit Plans (Details) - Pension and other post retirement benefit [Member] - Fair Value, Inputs, Level 3 [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of net plan assets as of the beginning of year	$ 12	$ 469
Relating to assets still held at the reporting date	0	(24)
Relating to assets sold during the period	0	(6)
Defined Benefit Plan Purchases	0	7
Settlements	0	53
Transfers into (out of) Level 3	(2)	(381)
Fair value of net plan assets as of the end of year	10	12
Debt Securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of net plan assets as of the beginning of year	12	337
Relating to assets still held at the reporting date	0	(9)
Relating to assets sold during the period	0	(19)
Defined Benefit Plan Purchases	0	0
Settlements	0	1
Transfers into (out of) Level 3	(3)	(296)
Fair value of net plan assets as of the end of year	9	12
Equity Securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of net plan assets as of the beginning of year	0	2
Relating to assets still held at the reporting date	0	0
Relating to assets sold during the period	0	0
Defined Benefit Plan Purchases	0	0
Settlements	0	0
Transfers into (out of) Level 3	1	(2)
Fair value of net plan assets as of the end of year	1	0
Private Placement [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of net plan assets as of the beginning of year	0	130
Relating to assets still held at the reporting date	0	(15)
Relating to assets sold during the period	0	13
Defined Benefit Plan Purchases	0	7
Settlements	0	52
Transfers into (out of) Level 3	0	(83)
Fair value of net plan assets as of the end of year	$ 0	$ 0