Fair Value (Quantitative Information) (Details)	Sep. 30, 2018	Dec. 31, 2017
Minimum | Interest rate contracts | Measurement Input, Swap Yield
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Asset (Liability) Net, Measurement Input	310	200
Minimum | Interest rate contracts | Measurement Input, Repurchase Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Asset (Liability) Net, Measurement Input	(5)	(5)
Minimum | Foreign currency exchange rate contracts | Measurement Input, Swap Yield
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Asset (Liability) Net, Measurement Input	(60)	(14)
Minimum | Credit contracts | Measurement Input, Credit Spread
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Asset (Liability) Net, Measurement Input	96	0
Minimum | Equity market contracts | Measurement Input, Price Volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Asset (Liability) Net, Measurement Input	0.11	0.11
Minimum | Equity market contracts | Measurement Input, Correlation
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Asset (Liability) Net, Measurement Input	0.10	0.10
Minimum | Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Measurement Input, Utilization Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative Asset (Liability) Net, Measurement Input	0.0000	0.0000
Minimum | Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Measurement Input, Withdrawal Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative Asset (Liability) Net, Measurement Input	0.0000	0.0000
Minimum | Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Measurement Input, Long-Term Equity Volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative Asset (Liability) Net, Measurement Input	0.0721	0.0825
Minimum | Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Measurement Input, Counterparty Credit Risk
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative Asset (Liability) Net, Measurement Input	0.0003	0.0002
Minimum | Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Durations 1 - 10 | Measurement Input, Lapse Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative Asset (Liability) Net, Measurement Input	0.0025	0.0025
Minimum | Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Durations 11 - 20 | Measurement Input, Lapse Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative Asset (Liability) Net, Measurement Input	0.0200	0.0200
Minimum | Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Durations 21 - 116 | Measurement Input, Lapse Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative Asset (Liability) Net, Measurement Input	0.0125	0.0125
Minimum | Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Ages 0 - 40 | Measurement Input, Mortality Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative Asset (Liability) Net, Measurement Input	0.0000	0.0000
Minimum | Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Ages 41 - 60 | Measurement Input, Mortality Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative Asset (Liability) Net, Measurement Input	0.0003	0.0003
Minimum | Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Ages 61 - 115 | Measurement Input, Mortality Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative Asset (Liability) Net, Measurement Input	0.0015	0.0015
Minimum | U.S. corporate and foreign corporate securities | Valuation Technique, Matrix Pricing | Measurement Input, Offered Price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	85	83
Minimum | U.S. corporate and foreign corporate securities | Valuation, Market Approach | Measurement Input, Quoted Price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	37	10
Minimum | U.S. corporate and foreign corporate securities | Valuation Technique, Consensus Pricing Model | Measurement Input, Offered Price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	98	97
Minimum | RMBS | Valuation, Market Approach | Measurement Input, Quoted Price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	0	0
Minimum | ABS | Valuation, Market Approach | Measurement Input, Quoted Price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	3	5
Minimum | ABS | Valuation Technique, Consensus Pricing Model | Measurement Input, Offered Price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	99	100
Maximum | Interest rate contracts | Measurement Input, Swap Yield
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Asset (Liability) Net, Measurement Input	331	300
Maximum | Interest rate contracts | Measurement Input, Repurchase Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Asset (Liability) Net, Measurement Input	55	5
Maximum | Foreign currency exchange rate contracts | Measurement Input, Swap Yield
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Asset (Liability) Net, Measurement Input	328	309
Maximum | Credit contracts | Measurement Input, Credit Spread
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Asset (Liability) Net, Measurement Input	100	0
Maximum | Equity market contracts | Measurement Input, Price Volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Asset (Liability) Net, Measurement Input	0.26	0.31
Maximum | Equity market contracts | Measurement Input, Correlation
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Asset (Liability) Net, Measurement Input	0.30	0.30
Maximum | Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Measurement Input, Utilization Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative Asset (Liability) Net, Measurement Input	0.2500	0.2500
Maximum | Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Measurement Input, Withdrawal Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative Asset (Liability) Net, Measurement Input	0.2000	0.2000
Maximum | Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Measurement Input, Long-Term Equity Volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative Asset (Liability) Net, Measurement Input	0.3300	0.3300
Maximum | Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Measurement Input, Counterparty Credit Risk
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative Asset (Liability) Net, Measurement Input	0.0151	0.0132
Maximum | Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Durations 1 - 10 | Measurement Input, Lapse Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative Asset (Liability) Net, Measurement Input	1.0000	1.0000
Maximum | Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Durations 11 - 20 | Measurement Input, Lapse Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative Asset (Liability) Net, Measurement Input	1.0000	1.0000
Maximum | Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Durations 21 - 116 | Measurement Input, Lapse Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative Asset (Liability) Net, Measurement Input	1.0000	1.0000
Maximum | Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Ages 0 - 40 | Measurement Input, Mortality Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative Asset (Liability) Net, Measurement Input	0.0021	0.0021
Maximum | Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Ages 41 - 60 | Measurement Input, Mortality Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative Asset (Liability) Net, Measurement Input	0.0080	0.0075
Maximum | Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Ages 61 - 115 | Measurement Input, Mortality Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative Asset (Liability) Net, Measurement Input	1.0000	1.0000
Maximum | U.S. corporate and foreign corporate securities | Valuation Technique, Matrix Pricing | Measurement Input, Offered Price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	126	142
Maximum | U.S. corporate and foreign corporate securities | Valuation, Market Approach | Measurement Input, Quoted Price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	703	443
Maximum | U.S. corporate and foreign corporate securities | Valuation Technique, Consensus Pricing Model | Measurement Input, Offered Price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	108	104
Maximum | RMBS | Valuation, Market Approach | Measurement Input, Quoted Price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	109	126
Maximum | ABS | Valuation, Market Approach | Measurement Input, Quoted Price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	117	117
Maximum | ABS | Valuation Technique, Consensus Pricing Model | Measurement Input, Offered Price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	102	103
Weighted Average | U.S. corporate and foreign corporate securities | Valuation Technique, Matrix Pricing | Measurement Input, Offered Price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	104	110
Weighted Average | U.S. corporate and foreign corporate securities | Valuation, Market Approach | Measurement Input, Quoted Price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	128	121
Weighted Average | U.S. corporate and foreign corporate securities | Valuation Technique, Consensus Pricing Model | Measurement Input, Offered Price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	100	101
Weighted Average | RMBS | Valuation, Market Approach | Measurement Input, Quoted Price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	94	94
Weighted Average | ABS | Valuation, Market Approach | Measurement Input, Quoted Price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	100	100
Weighted Average | ABS | Valuation Technique, Consensus Pricing Model | Measurement Input, Offered Price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Measurement Input	100	100