Investments (Investments in Fixed Maturity Securities Available-for-Sale by Sector) (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Fixed maturity securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 52,797	$ 49,548
Financing Receivable, Allowance for Credit Loss	16	20
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	5,773	7,404
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	267	197
Estimated Fair Value	$ 58,287	$ 56,735
% of Total	100.00%	100.00%
Corporate Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 33,687	$ 31,963
Estimated Fair Value	$ 37,004	$ 36,208
% of Total	100.00%	100.00%
Corporate Debt Securities [Member] \| Fixed maturity securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 33,687	$ 31,963
Financing Receivable, Allowance for Credit Loss	11	17
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	3,465	4,356
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	137	94
Estimated Fair Value	$ 37,004	$ 36,208
% of Total	63.40%	63.90%
Canadian and Canadian provincial governments \| Fixed maturity securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 3,303	$ 3,145
Financing Receivable, Allowance for Credit Loss	0	0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	1,602	1,995
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	2	0
Estimated Fair Value	$ 4,903	$ 5,140
% of Total	8.40%	9.10%
Residential mortgage-backed securities \| Fixed maturity securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,323	$ 1,735
Financing Receivable, Allowance for Credit Loss	0	0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	60	84
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	6	2
Estimated Fair Value	$ 1,377	$ 1,817
% of Total	2.40%	3.20%
Asset-backed securities \| Fixed maturity securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 3,467	$ 3,099
Financing Receivable, Allowance for Credit Loss	0	0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	36	35
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	21	42
Estimated Fair Value	$ 3,482	$ 3,092
% of Total	6.00%	5.40%
Commercial Mortgage Backed Securities [Member] \| Fixed maturity securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,774	$ 1,790
Financing Receivable, Allowance for Credit Loss	1	3
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	102	102
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	6	21
Estimated Fair Value	$ 1,869	$ 1,868
% of Total	3.20%	3.30%
US Treasury and Government [Member] \| Fixed maturity securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,295	$ 1,242
Financing Receivable, Allowance for Credit Loss	0	0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	47	196
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	24	1
Estimated Fair Value	$ 1,318	$ 1,437
% of Total	2.30%	2.50%
US States and Political Subdivisions Debt Securities [Member] \| Fixed maturity securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,206	$ 1,237
Financing Receivable, Allowance for Credit Loss	0	0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	144	157
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	6	4
Estimated Fair Value	$ 1,344	$ 1,390
% of Total	2.30%	2.40%
Debt Security, Government, Non-US [Member] \| Fixed maturity securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 6,742	$ 5,337
Financing Receivable, Allowance for Credit Loss	4	0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	317	479
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	65	33
Estimated Fair Value	$ 6,990	$ 5,783
% of Total	12.00%	10.20%

Percentage of available for sale securities

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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