Investments - Credit Risk Profile, Commercial Mortgage Loans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	2,010	2,081
Weighted Average [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Debt service coverage ratio, commercial mortgage loans	1.70	1.66
Loan-to-value ratio, commercial mortgage loans	61.00%	63.00%
Loan To Value Ratio Below 50 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	362	363
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	675	719
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	532	469
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	215	217
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	109	105
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	117	208
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	1,507	1,489
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	338	340
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	638	681
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	457	394
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	68	68
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	6	6
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	132	132
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	18	17
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	37	38
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	0	0
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	36	36
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	41	41
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	102	103
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	0	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	15	15
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	32	33
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	55	55
Debt Service Coverage Ratio 1.00x To 1.09x [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	6	6
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	6	6
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	0	0
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	0
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	0
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	0	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	263	351
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	60	60
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	79	80
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	62	58
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	62	153