Fair Value of Assets and Liabilities Fair Value of Assets and Liabilities (Financial Instruments where Carrying Amounts and Fair Values May Differ) (Details) - USD ($) $ in Millions		Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Assets
Mortgage loans on real estate (net of valuation allowances)		$ 6,014	$ 5,706
Policy loans		1,314	1,319
Funds withheld at interest		5,258	5,662
Cash and cash equivalents		2,820	1,449	$ 2,020	$ 1,890
Short-term investments		117	64
Other invested assets		2,542	2,363
Accrued investment income		510	493
Liabilities
Interest-sensitive contract liabilities		23,164	22,711
Long-term debt		2,981	2,981
Collateral finance and securitization notes		569	598
Reported Value Measurement [Member]
Assets
Mortgage loans on real estate (net of valuation allowances)	[1]	6,014	5,706
Policy loans	[1]	1,314	1,319
Funds withheld at interest	[1]	5,345	5,526
Cash and cash equivalents	[1]	1,702	1,175
Short-term investments	[1]	32	32
Other invested assets	[1]	1,282	1,259
Accrued investment income	[1]	510	493
Liabilities
Interest-sensitive contract liabilities	[1]	19,634	19,163
Long-term debt	[1]	2,981
Debt, Long-term and Short-term, Combined Amount	[1]		2,981
Collateral finance and securitization notes	[1]	569	598
Estimate of Fair Value Measurement [Member]
Assets
Mortgage loans on real estate (net of valuation allowances)		6,123	5,935
Policy loans		1,314	1,319
Funds withheld at interest		5,603	5,870
Cash and cash equivalents		1,702	1,175
Short-term investments		32	32
Other invested assets		1,363	1,278
Accrued investment income		510	493
Liabilities
Interest-sensitive contract liabilities		20,503	21,542
Long-term Debt, Fair Value		2,932
Debt, Long-term and Short-term, Combined Amount			3,179
Collateral finance and securitization notes		524	551
Estimate of Fair Value Measurement [Member] | Net Asset Value [Member]
Assets
Mortgage loans on real estate (net of valuation allowances)			0
Policy loans			0
Funds withheld at interest			0
Cash and cash equivalents			0
Short-term investments			0
Other invested assets		430	402
Accrued investment income			0
Liabilities
Interest-sensitive contract liabilities			0
Debt, Long-term and Short-term, Combined Amount			0
Collateral finance and securitization notes			0
Estimate of Fair Value Measurement [Member] | Fair Value Inputs Level 1 Member
Assets
Mortgage loans on real estate (net of valuation allowances)		0	0
Policy loans		0	0
Funds withheld at interest		0	0
Cash and cash equivalents		1,702	1,175
Short-term investments		32	32
Other invested assets		5	5
Accrued investment income		0	0
Liabilities
Interest-sensitive contract liabilities		0	0
Long-term Debt, Fair Value		0
Debt, Long-term and Short-term, Combined Amount			0
Collateral finance and securitization notes		0	0
Estimate of Fair Value Measurement [Member] | Fair Value Inputs Level 2 Member
Assets
Mortgage loans on real estate (net of valuation allowances)		0	0
Policy loans		1,314	1,319
Funds withheld at interest		0	0
Cash and cash equivalents		0	0
Short-term investments		0	0
Other invested assets		91	68
Accrued investment income		510	493
Liabilities
Interest-sensitive contract liabilities		20,503	0
Long-term Debt, Fair Value		2,932
Debt, Long-term and Short-term, Combined Amount			0
Collateral finance and securitization notes		524	0
Estimate of Fair Value Measurement [Member] | Fair Value Inputs Level 3 Member
Assets
Mortgage loans on real estate (net of valuation allowances)		6,123	5,935
Policy loans		0	0
Funds withheld at interest		5,603	5,870
Cash and cash equivalents		0	0
Short-term investments		0	0
Other invested assets		837	803
Accrued investment income		0	0
Liabilities
Interest-sensitive contract liabilities		0	21,542
Long-term Debt, Fair Value		0
Debt, Long-term and Short-term, Combined Amount			3,179
Collateral finance and securitization notes		0	$ 551
Estimate of Fair Value Measurement [Member] | Fair Value Inputs Level 3 Member | Net Asset Value [Member]
Assets
Mortgage loans on real estate (net of valuation allowances)		0
Policy loans		0
Funds withheld at interest		0
Cash and cash equivalents		0
Short-term investments		0
Accrued investment income		0
Liabilities
Interest-sensitive contract liabilities		0
Long-term Debt, Fair Value		0
Collateral finance and securitization notes		$ 0

[1] Carrying values presented herein may differ from those in the Company’s condensed consolidated balance sheets because certain items within the respective financial statement captions may be measured at fair value on a recurring basis.