Investments - Credit Risk Profile, Commercial Mortgage Loans (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	2,081	2,252
Weighted Average [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Debt service coverage ratio, commercial mortgage loans	1.66	1.62
Loan-to-value ratio, commercial mortgage loans	63.00%	64.00%
Loan To Value Ratio Below 50 Percent [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	363	320
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	719	730
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	469	507
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	217	192
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	105	312
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	208	191
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	1,489	1,477
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	340	314
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	681	581
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	394	438
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	79
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	65
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	302
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	17	0
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	38	131
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	16
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	113
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	42
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	103	121
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	29
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	33	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	34
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	58
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	102
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	18
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	28
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	50
Debt Service Coverage Ratio Less Than 1.00x [Member]
Schedule Of Financing Receivable Recorded Investment Credit Quality Indicator [Line Items]
Commercial mortgage loan	351	250
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	24
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	80	0
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	58	143
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	153	83