Investments (Internal Credit Quality Indicators) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 5,861	$ 5,727
High Investment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	3,438
Internal Investment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	2,271
Average Investment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	111
Watch List
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	4
Internal Noninvestment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	37
Year Of Origination 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	763
Year Of Origination 2020 | High Investment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	411
Year Of Origination 2020 | Internal Investment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	352
Year Of Origination 2020 | Average Investment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	0
Year Of Origination 2020 | Watch List
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	0
Year Of Origination 2020 | Internal Noninvestment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	0
Year Of Origination 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	1,112
Year Of Origination 2019 | High Investment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	616
Year Of Origination 2019 | Internal Investment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	496
Year Of Origination 2019 | Average Investment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	0
Year Of Origination 2019 | Watch List
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	0
Year Of Origination 2019 | Internal Noninvestment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	0
Year Of Origination 2018
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	892
Year Of Origination 2018 | High Investment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	493
Year Of Origination 2018 | Internal Investment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	399
Year Of Origination 2018 | Average Investment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	0
Year Of Origination 2018 | Watch List
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	0
Year Of Origination 2018 | Internal Noninvestment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	0
Year Of Origination 2017
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	762
Year Of Origination 2017 | High Investment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	336
Year Of Origination 2017 | Internal Investment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	407
Year Of Origination 2017 | Average Investment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	19
Year Of Origination 2017 | Watch List
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	0
Year Of Origination 2017 | Internal Noninvestment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	0
Year Of Origination 2016
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	860
Year Of Origination 2016 | High Investment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	574
Year Of Origination 2016 | Internal Investment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	249
Year Of Origination 2016 | Average Investment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	37
Year Of Origination 2016 | Watch List
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	0
Year Of Origination 2016 | Internal Noninvestment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	0
Year Of Origination Prior Periods
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	1,472
Year Of Origination Prior Periods | High Investment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	1,008
Year Of Origination Prior Periods | Internal Investment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	368
Year Of Origination Prior Periods | Average Investment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	55
Year Of Origination Prior Periods | Watch List
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	4
Year Of Origination Prior Periods | Internal Noninvestment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 37