Investments Investments (Internal Credit Rating Disclosure) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 6,063	$ 5,727
Allowance for Loan and Lease Losses, Real Estate	39	$ 12	$ 11	$ 11
High Investment Grade [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,783
Internal Investment Grade [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,102
Average Investment Grade [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	157
Watch List [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	4
Internal Noninvestment Grade [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	17
Year Of Origination 2020 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	538
Year Of Origination 2020 [Member] | High Investment Grade [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	302
Year Of Origination 2020 [Member] | Internal Investment Grade [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	236
Year Of Origination 2020 [Member] | Average Investment Grade [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Year Of Origination 2020 [Member] | Watch List [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Year Of Origination 2020 [Member] | Internal Noninvestment Grade [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Year Of Origination 2019 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,191
Year Of Origination 2019 [Member] | High Investment Grade [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	675
Year Of Origination 2019 [Member] | Internal Investment Grade [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	516
Year Of Origination 2019 [Member] | Average Investment Grade [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Year Of Origination 2019 [Member] | Watch List [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Year Of Origination 2019 [Member] | Internal Noninvestment Grade [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Year Of Origination 2018 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	950
Year Of Origination 2018 [Member] | High Investment Grade [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	623
Year Of Origination 2018 [Member] | Internal Investment Grade [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	317
Year Of Origination 2018 [Member] | Average Investment Grade [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	10
Year Of Origination 2018 [Member] | Watch List [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Year Of Origination 2018 [Member] | Internal Noninvestment Grade [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Year Of Origination 2017 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	770
Year Of Origination 2017 [Member] | High Investment Grade [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	403
Year Of Origination 2017 [Member] | Internal Investment Grade [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	342
Year Of Origination 2017 [Member] | Average Investment Grade [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	25
Year Of Origination 2017 [Member] | Watch List [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Year Of Origination 2017 [Member] | Internal Noninvestment Grade [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Year Of Origination 2016 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	899
Year Of Origination 2016 [Member] | High Investment Grade [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	603
Year Of Origination 2016 [Member] | Internal Investment Grade [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	269
Year Of Origination 2016 [Member] | Average Investment Grade [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	27
Year Of Origination 2016 [Member] | Watch List [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Year Of Origination 2016 [Member] | Internal Noninvestment Grade [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Year Of Origination Prior Periods [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,715
Year Of Origination Prior Periods [Member] | High Investment Grade [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,177
Year Of Origination Prior Periods [Member] | Internal Investment Grade [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	422
Year Of Origination Prior Periods [Member] | Average Investment Grade [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	95
Year Of Origination Prior Periods [Member] | Watch List [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	4
Year Of Origination Prior Periods [Member] | Internal Noninvestment Grade [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 17