Fair Value of Assets and Liabilities (Balances of Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions	Jun. 30, 2021		Dec. 31, 2020
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	$ 58,287		$ 56,735
Equity Method Investments, Fair Value Disclosure	147		132
Funds withheld at interest embedded derivatives	206		114
Cash and cash equivalents	1,167		1,478
Short-term investments	166		197
Derivative Assets (Liabilities), at Fair Value, Net			140
Investments, Fair Value Disclosure	253	[1]	429
Assets, Fair Value Disclosure	60,226		59,085
Fair Value Measured On Recurring Basis Guaranteed Interest Contracts Embedded Derivatives	880		907
Liabilities Fair Value Disclosure
Other liabilities			(49)
Financial Liabilities Fair Value Disclosure	924		956
Fair Value, Net Asset (Liability)	493
Other
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	53
Interest Rate Swap [Member]
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	146
Liabilities Fair Value Disclosure
Other liabilities	(44)
Fair Value Option Contractholder Directed Unit Linked Investments [Member]
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	54		289
Corporate Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	37,004		36,208
Canadian and Canadian provincial governments
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	4,903		5,140
Residential mortgage-backed securities
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	1,377		1,817
Asset-backed securities
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	3,482		3,092
Assets, Fair Value Disclosure	78		87
Commercial Mortgage Backed Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	1,869		1,868
US Government Agencies Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	1,318		1,437
Assets, Fair Value Disclosure	13		14
US States and Political Subdivisions Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	1,344		1,390
Debt Security, Government, Non-US [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	6,990		5,783
Fair Value Inputs Level 1 Member
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	1,198		1,312
Equity Method Investments, Fair Value Disclosure	84		79
Funds withheld at interest embedded derivatives	0		0
Cash and cash equivalents	1,152		1,478
Short-term investments	1		32
Derivative Assets (Liabilities), at Fair Value, Net			0
Investments, Fair Value Disclosure	0	[1]	224
Assets, Fair Value Disclosure	2,435		3,125
Fair Value Measured On Recurring Basis Guaranteed Interest Contracts Embedded Derivatives	0		0
Liabilities Fair Value Disclosure
Other liabilities			0
Financial Liabilities Fair Value Disclosure	0		0
Fair Value Inputs Level 1 Member | Other
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	0
Fair Value Inputs Level 1 Member | Interest Rate Swap [Member]
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	0
Liabilities Fair Value Disclosure
Other liabilities	0
Fair Value Inputs Level 1 Member | Fair Value Option Contractholder Directed Unit Linked Investments [Member]
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	0		224
Fair Value Inputs Level 1 Member | Corporate Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	0		0
Fair Value Inputs Level 1 Member | Canadian and Canadian provincial governments
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	0		0
Fair Value Inputs Level 1 Member | Residential mortgage-backed securities
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	0		0
Fair Value Inputs Level 1 Member | Asset-backed securities
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	0		0
Fair Value Inputs Level 1 Member | Commercial Mortgage Backed Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	0		0
Fair Value Inputs Level 1 Member | US Government Agencies Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	1,198		1,312
Fair Value Inputs Level 1 Member | US States and Political Subdivisions Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	0		0
Fair Value Inputs Level 1 Member | Debt Security, Government, Non-US [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	0		0
Fair Value Inputs Level 2 Member
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	53,166		52,100
Equity Method Investments, Fair Value Disclosure	0		0
Funds withheld at interest embedded derivatives	0		0
Cash and cash equivalents	15		0
Short-term investments	165		150
Derivative Assets (Liabilities), at Fair Value, Net			140
Investments, Fair Value Disclosure	253	[1]	205
Assets, Fair Value Disclosure	53,599		52,455
Fair Value Measured On Recurring Basis Guaranteed Interest Contracts Embedded Derivatives	0		0
Liabilities Fair Value Disclosure
Other liabilities			(49)
Financial Liabilities Fair Value Disclosure	44		49
Fair Value Inputs Level 2 Member | Other
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	53
Fair Value Inputs Level 2 Member | Interest Rate Swap [Member]
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	146
Liabilities Fair Value Disclosure
Other liabilities	(44)
Fair Value Inputs Level 2 Member | Fair Value Option Contractholder Directed Unit Linked Investments [Member]
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	54		65
Fair Value Inputs Level 2 Member | Corporate Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	33,796		33,179
Fair Value Inputs Level 2 Member | Canadian and Canadian provincial governments
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	4,903		5,140
Fair Value Inputs Level 2 Member | Residential mortgage-backed securities
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	1,375		1,814
Fair Value Inputs Level 2 Member | Asset-backed securities
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	2,896		2,896
Fair Value Inputs Level 2 Member | Commercial Mortgage Backed Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	1,804		1,813
Fair Value Inputs Level 2 Member | US Government Agencies Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	107		111
Fair Value Inputs Level 2 Member | US States and Political Subdivisions Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	1,336		1,381
Fair Value Inputs Level 2 Member | Debt Security, Government, Non-US [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	6,949		5,766
Fair Value Inputs Level 3 Member
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	3,923		3,323
Equity Method Investments, Fair Value Disclosure	63		53
Funds withheld at interest embedded derivatives	206		114
Cash and cash equivalents	0		0
Short-term investments	0		15
Derivative Assets (Liabilities), at Fair Value, Net			0
Investments, Fair Value Disclosure	0	[1]	0
Assets, Fair Value Disclosure	4,192		3,505
Fair Value Measured On Recurring Basis Guaranteed Interest Contracts Embedded Derivatives	880		907
Liabilities Fair Value Disclosure
Other liabilities			0
Financial Liabilities Fair Value Disclosure	880		907
Fair Value Inputs Level 3 Member | Other
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	0
Fair Value Inputs Level 3 Member | Interest Rate Swap [Member]
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	0
Liabilities Fair Value Disclosure
Other liabilities	0
Fair Value Inputs Level 3 Member | Fair Value Option Contractholder Directed Unit Linked Investments [Member]
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	0		0
Fair Value Inputs Level 3 Member | Corporate Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	3,208		3,029
Fair Value Inputs Level 3 Member | Canadian and Canadian provincial governments
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	0		0
Fair Value Inputs Level 3 Member | Residential mortgage-backed securities
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	2		3
Fair Value Inputs Level 3 Member | Asset-backed securities
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	586		196
Fair Value Inputs Level 3 Member | Commercial Mortgage Backed Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	65		55
Fair Value Inputs Level 3 Member | US Government Agencies Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	13		14
Fair Value Inputs Level 3 Member | US States and Political Subdivisions Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	8		9
Fair Value Inputs Level 3 Member | Debt Security, Government, Non-US [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	$ 41		$ 17

[1] Other invested assets included in the fair value hierarchy exclude limited partnership interests that are measured at estimated fair value using the net asset value (“NAV”) per share (or its equivalent) as a practical expedient. As of June 30, 2021, the fair value of such investments was $493 million.