Pension Plans, Retirement Benefits and Savings Plans (Details) - Additional Pension Disclosures - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income:
Total other changes in benefit plan assets and benefit obligations recognized in other comprehensive income	$ (455)	$ (18)	$ (33)
Pension Plans [Member]
Defined benefit plan disclosure
Total accumulated benefit obligation	4,250	4,400
Aggregate projected benefit obligation for plans with a projected benefit obligation in excess of plan assets	131	250
Aggregate plan assets for plans with a projected benefit obligation in excess of plan assets	0	109
Aggregate accumulated benefit obligation for plans with an accumulated benefit obligation in excess of plan assets	118	239
Aggregate plan assets for plans with an accumulated benefit obligation in excess of plan assets	0	109
Actuarial gain (loss)	75	(356)
Company contributions	12	9
Components of net periodic benefit cost (benefit)
Service cost	141	133	118
Interest cost on benefit obligation	83	114	141
Expected return on plan assets	(274)	(275)	(275)
Net periodic benefit cost (benefit), amortization of unrecognized prior service benefit	(1)	(1)	(1)
Net periodic benefit cost (benefit), amortization of unrecognized net actuarial (gain) loss	109	93	56
Total non-service cost (benefit)	(83)	(69)	(79)
Net periodic benefit cost (benefit)	58	64	39
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income:
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income, prior service benefit	0	1	0
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income, net actuarial (gain) loss	(338)	61	49
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income, foreign currency exchange rate change	0	1	1
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income, amortization of prior service benefit	1	1	1
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income, amortization of net actuarial gain (loss)	(109)	(93)	(56)
Total other changes in benefit plan assets and benefit obligations recognized in other comprehensive income	(446)	(29)	(5)
Total other changes recognized in net periodic benefit cost and other comprehensive income	(388)	35	34
Pension Plans [Member] | Net investment income [Member]
Components of net periodic benefit cost (benefit)
Service cost	1	1	1
Pension Plans [Member] | Claims and claim adjustment expenses [Member]
Components of net periodic benefit cost (benefit)
Service cost	57	55	48
Total non-service cost (benefit)	(34)	(29)	(33)
Pension Plans [Member] | General and administrative expenses [Member]
Components of net periodic benefit cost (benefit)
Service cost	83	77	69
Total non-service cost (benefit)	(49)	(40)	(46)
Pension Plans [Member] | United States [Member] | Qualified Plan [Member]
Defined benefit plan disclosure
Total accumulated benefit obligation	4,000	4,150
Actuarial gain (loss)	73	(336)
Required contributions made	0	0	0
Company contributions	0	0	0
Required contributions during next fiscal year	0
Components of net periodic benefit cost (benefit)
Service cost	135	128
Interest cost on benefit obligation	79	109
Nonqualified and Foreign Pension Plans [Member]
Defined benefit plan disclosure
Total accumulated benefit obligation	246	253
Actuarial gain (loss)	2	(20)
Company contributions	12	9
Components of net periodic benefit cost (benefit)
Service cost	6	5
Interest cost on benefit obligation	4	5
Postretirement Benefit Plans [Member]
Defined benefit plan disclosure
Aggregate accumulated benefit obligation for plans with an accumulated benefit obligation in excess of plan assets	149	171
Aggregate plan assets for plans with an accumulated benefit obligation in excess of plan assets	9	11
Actuarial gain (loss)	16	(5)
Company contributions	7	8
Components of net periodic benefit cost (benefit)
Service cost	0	0	0
Interest cost on benefit obligation	3	4	7
Expected return on plan assets	0	0	(1)
Net periodic benefit cost (benefit), amortization of unrecognized prior service benefit	(4)	(3)	(3)
Net periodic benefit cost (benefit), amortization of unrecognized net actuarial (gain) loss	(2)	(4)	0
Total non-service cost (benefit)	(3)	(3)	3
Net periodic benefit cost (benefit)	(3)	(3)	3
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income:
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income, prior service benefit	0	0	0
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income, net actuarial (gain) loss	(16)	4	(31)
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income, foreign currency exchange rate change	0	0	0
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income, amortization of prior service benefit	4	3	3
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income, amortization of net actuarial gain (loss)	2	4	0
Total other changes in benefit plan assets and benefit obligations recognized in other comprehensive income	(10)	11	(28)
Total other changes recognized in net periodic benefit cost and other comprehensive income	(13)	8	(25)
Postretirement Benefit Plans [Member] | Net investment income [Member]
Components of net periodic benefit cost (benefit)
Service cost	0	0	0
Postretirement Benefit Plans [Member] | Claims and claim adjustment expenses [Member]
Components of net periodic benefit cost (benefit)
Service cost	0	0	0
Total non-service cost (benefit)	(1)	(1)	1
Postretirement Benefit Plans [Member] | General and administrative expenses [Member]
Components of net periodic benefit cost (benefit)
Service cost	0	0	0
Total non-service cost (benefit)	$ (2)	$ (2)	$ 2