Claim, Claim Adjustment Expense and Future Policy Benefit Reserves (International - Excluding Hardy - Net Cumulative Paid Claim and Claim Adjustment Expenses) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Total net liability for unpaid claim and claim adjustment expenses	$ 19,205	$ 18,701	$ 17,885	$ 17,965
International
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Total net liability for unpaid claim and claim adjustment expenses	1,940	1,822
Excluding Hardy | International
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Cumulative paid claims and allocated claim adjustment expense, net	2,053
Net liability for unpaid claim and allocated claim adjustment expenses for the accident years presented	1,318
Net liability for unpaid claim and claim adjustment expenses for accident years prior to 2012	47
Liability for unallocated claim adjustment expenses for accident years presented	35
Total net liability for unpaid claim and claim adjustment expenses	1,400
Excluding Hardy | 2012 | International
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Cumulative paid claims and allocated claim adjustment expense, net	218	215	213	210	$ 200	$ 188	$ 172	$ 151	$ 117	$ 46
Excluding Hardy | 2013 | International
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Cumulative paid claims and allocated claim adjustment expense, net	224	218	206	186	176	161	144	116	$ 51
Excluding Hardy | 2014 | International
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Cumulative paid claims and allocated claim adjustment expense, net	250	245	211	190	173	154	126	$ 54
Excluding Hardy | 2015 | International
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Cumulative paid claims and allocated claim adjustment expense, net	239	228	213	189	168	137	$ 58
Excluding Hardy | 2016 | International
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Cumulative paid claims and allocated claim adjustment expense, net	223	200	188	164	136	$ 68
Excluding Hardy | 2017 | International
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Cumulative paid claims and allocated claim adjustment expense, net	247	223	193	152	$ 67
Excluding Hardy | 2018 | International
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Cumulative paid claims and allocated claim adjustment expense, net	252	221	173	$ 94
Excluding Hardy | 2019 | International
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Cumulative paid claims and allocated claim adjustment expense, net	209	171	$ 76
Excluding Hardy | 2020 | International
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Cumulative paid claims and allocated claim adjustment expense, net	133	$ 62
Excluding Hardy | 2021 | International
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Cumulative paid claims and allocated claim adjustment expense, net	$ 58