Investments - Credit Risk Profile, Commercial Mortgage Loans (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2015
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	$ 1,814	$ 1,864
Weighted Average [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Debt service coverage ratio, commercial mortgage loans	1.88	1.78
Loan-to-value ratio, commercial mortgage loans	57.00%	58.00%
Loan To Value Ratio Below 50 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	$ 498	$ 330
Loan To Value Ratio Below 50 Percent [Member] | Maximum [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Loan-to-value ratio, commercial mortgage loans	50.00%	50.00%
Loan To Value Ratio 50 Percent To 59 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	$ 583	$ 707
Loan To Value Ratio 50 Percent To 59 Percent [Member] | Maximum [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Loan-to-value ratio, commercial mortgage loans	59.00%	59.00%
Loan To Value Ratio 50 Percent To 59 Percent [Member] | Minimum [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Loan-to-value ratio, commercial mortgage loans	50.00%	50.00%
Loan To Value Ratio 60 Percent To 69 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	$ 556	$ 623
Loan To Value Ratio 60 Percent To 69 Percent [Member] | Maximum [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Loan-to-value ratio, commercial mortgage loans	69.00%	69.00%
Loan To Value Ratio 60 Percent To 69 Percent [Member] | Minimum [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Loan-to-value ratio, commercial mortgage loans	60.00%	60.00%
Loan To Value Ratio 70 Percent To 79 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	$ 65	$ 66
Loan To Value Ratio 70 Percent To 79 Percent [Member] | Maximum [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Loan-to-value ratio, commercial mortgage loans	79.00%	79.00%
Loan To Value Ratio 70 Percent To 79 Percent [Member] | Minimum [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Loan-to-value ratio, commercial mortgage loans	70.00%	70.00%
Loan To Value Ratio 80 Percent To 89 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	$ 40	$ 40
Loan To Value Ratio 80 Percent To 89 Percent [Member] | Maximum [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Loan-to-value ratio, commercial mortgage loans	89.00%	89.00%
Loan To Value Ratio 80 Percent To 89 Percent [Member] | Minimum [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Loan-to-value ratio, commercial mortgage loans	80.00%	80.00%
Loan To Value Ratio 90 Percent To 100 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	$ 72	$ 98
Loan To Value Ratio 90 Percent To 100 Percent [Member] | Maximum [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Loan-to-value ratio, commercial mortgage loans	100.00%	100.00%
Loan To Value Ratio 90 Percent To 100 Percent [Member] | Minimum [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Loan-to-value ratio, commercial mortgage loans	90.00%	90.00%
Debt Service Coverage Ratio 1.30x Or Greater [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	$ 1,526	$ 1,574
Debt Service Coverage Ratio 1.30x Or Greater [Member] | Minimum [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Debt service coverage ratio, commercial mortgage loans	1.30	1.30
Debt Service Coverage Ratio 1.30x Or Greater [Member] | Loan To Value Ratio Below 50 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	$ 482	$ 261
Debt Service Coverage Ratio 1.30x Or Greater [Member] | Loan To Value Ratio 50 Percent To 59 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	502	683
Debt Service Coverage Ratio 1.30x Or Greater [Member] | Loan To Value Ratio 60 Percent To 69 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	542	590
Debt Service Coverage Ratio 1.30x Or Greater [Member] | Loan To Value Ratio 70 Percent To 79 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	0	0
Debt Service Coverage Ratio 1.30x Or Greater [Member] | Loan To Value Ratio 80 Percent To 89 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	0	40
Debt Service Coverage Ratio 1.30x Or Greater [Member] | Loan To Value Ratio 90 Percent To 100 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	0	0
Debt Service Coverage Ratio 1.20x To 1.29x [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	$ 54	$ 16
Debt Service Coverage Ratio 1.20x To 1.29x [Member] | Maximum [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Debt service coverage ratio, commercial mortgage loans	1.29	1.29
Debt Service Coverage Ratio 1.20x To 1.29x [Member] | Minimum [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Debt service coverage ratio, commercial mortgage loans	1.20	1.20
Debt Service Coverage Ratio 1.20x To 1.29x [Member] | Loan To Value Ratio Below 50 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	$ 16	$ 2
Debt Service Coverage Ratio 1.20x To 1.29x [Member] | Loan To Value Ratio 50 Percent To 59 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	24	0
Debt Service Coverage Ratio 1.20x To 1.29x [Member] | Loan To Value Ratio 60 Percent To 69 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	14	14
Debt Service Coverage Ratio 1.20x To 1.29x [Member] | Loan To Value Ratio 70 Percent To 79 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	0	0
Debt Service Coverage Ratio 1.20x To 1.29x [Member] | Loan To Value Ratio 80 Percent To 89 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	0	0
Debt Service Coverage Ratio 1.20x To 1.29x [Member] | Loan To Value Ratio 90 Percent To 100 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	0	0
Debt Service Coverage Ratio 1.10x To 1.19x [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	$ 49	$ 0
Debt Service Coverage Ratio 1.10x To 1.19x [Member] | Maximum [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Debt service coverage ratio, commercial mortgage loans	1.19	1.19
Debt Service Coverage Ratio 1.10x To 1.19x [Member] | Minimum [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Debt service coverage ratio, commercial mortgage loans	1.10	1.10
Debt Service Coverage Ratio 1.10x To 1.19x [Member] | Loan To Value Ratio Below 50 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	$ 0	$ 0
Debt Service Coverage Ratio 1.10x To 1.19x [Member] | Loan To Value Ratio 50 Percent To 59 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	19	0
Debt Service Coverage Ratio 1.10x To 1.19x [Member] | Loan To Value Ratio 60 Percent To 69 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	0	0
Debt Service Coverage Ratio 1.10x To 1.19x [Member] | Loan To Value Ratio 70 Percent To 79 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	30	0
Debt Service Coverage Ratio 1.10x To 1.19x [Member] | Loan To Value Ratio 80 Percent To 89 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	0	0
Debt Service Coverage Ratio 1.10x To 1.19x [Member] | Loan To Value Ratio 90 Percent To 100 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	0	0
Debt Service Coverage Ratio 1.00x To 1.09x [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	$ 78	$ 140
Debt Service Coverage Ratio 1.00x To 1.09x [Member] | Maximum [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Debt service coverage ratio, commercial mortgage loans	1.09	1.09
Debt Service Coverage Ratio 1.00x To 1.09x [Member] | Minimum [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Debt service coverage ratio, commercial mortgage loans	1.00	1.00
Debt Service Coverage Ratio 1.00x To 1.09x [Member] | Loan To Value Ratio Below 50 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	$ 0	$ 67
Debt Service Coverage Ratio 1.00x To 1.09x [Member] | Loan To Value Ratio 50 Percent To 59 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	38	24
Debt Service Coverage Ratio 1.00x To 1.09x [Member] | Loan To Value Ratio 60 Percent To 69 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	0	19
Debt Service Coverage Ratio 1.00x To 1.09x [Member] | Loan To Value Ratio 70 Percent To 79 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	0	30
Debt Service Coverage Ratio 1.00x To 1.09x [Member] | Loan To Value Ratio 80 Percent To 89 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	40	0
Debt Service Coverage Ratio 1.00x To 1.09x [Member] | Loan To Value Ratio 90 Percent To 100 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	0	0
Debt Service Coverage Ratio Less Than 1.00x [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	$ 107	$ 134
Debt Service Coverage Ratio Less Than 1.00x [Member] | Maximum [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Debt service coverage ratio, commercial mortgage loans	1.00	1.00
Debt Service Coverage Ratio Less Than 1.00x [Member] | Loan To Value Ratio Below 50 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	$ 0	$ 0
Debt Service Coverage Ratio Less Than 1.00x [Member] | Loan To Value Ratio 50 Percent To 59 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	0	0
Debt Service Coverage Ratio Less Than 1.00x [Member] | Loan To Value Ratio 60 Percent To 69 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	0	0
Debt Service Coverage Ratio Less Than 1.00x [Member] | Loan To Value Ratio 70 Percent To 79 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	35	36
Debt Service Coverage Ratio Less Than 1.00x [Member] | Loan To Value Ratio 80 Percent To 89 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	0	0
Debt Service Coverage Ratio Less Than 1.00x [Member] | Loan To Value Ratio 90 Percent To 100 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	$ 72	$ 98