Fair Value (Carrying amount and estimated fair value of financial instrument assets and liabilities which are not measured at fair value) (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Assets
Mortgage loans	$ 942	$ 973
Liabilities
Long term debt	2,779	2,779
Carrying Amount
Assets
Mortgage loans	942	973
Liabilities
Long term debt	2,779	2,779
Estimated Fair Value
Assets
Mortgage loans	940	1,018
Liabilities
Long term debt	2,795	2,978
Level 1 | Estimated Fair Value
Assets
Mortgage loans	0	0
Liabilities
Long term debt	0	0
Level 2 | Estimated Fair Value
Assets
Mortgage loans	0	0
Liabilities
Long term debt	2,795	2,978
Level 3 | Estimated Fair Value
Assets
Mortgage loans	940	1,018
Liabilities
Long term debt	$ 0	$ 0