Fair Value, Financial Assets and Liabilities Not Measured at Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2021		Dec. 31, 2020
Carrying Amount [Member]
Assets [Abstract]
Other invested assets, primarily mortgage loans	$ 1,043		$ 1,068
Liabilities [Abstract]
Short term debt	140	[1]	35
Long term debt	8,990	[1]	10,042
Estimated Fair Value [Member]
Assets [Abstract]
Other invested assets, primarily mortgage loans	1,107		1,151
Liabilities [Abstract]
Short term debt	144	[1]	36
Long term debt	9,826	[1]	11,247
Estimated Fair Value [Member] | Level 2 [Member]
Liabilities [Abstract]
Short term debt			19
Long term debt	9,204	[1]	10,482
Estimated Fair Value [Member] | Level 3 [Member]
Assets [Abstract]
Other invested assets, primarily mortgage loans	1,107		1,151
Liabilities [Abstract]
Short term debt	144	[1]	17
Long term debt	$ 622	[1]	$ 765

[1] As of March 31, 2021, Short and Long term debt exclude amounts classified as held for sale. See Note 2 for further discussion.