Fair Value (Quantitative Information) (Details) - $ / shares	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Interest rate contracts | Minimum | Income Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Swap yield	2.00%	2.00%
Repurchase Rate	(0.14%)	(0.44%)
Interest rate contracts | Maximum | Income Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Swap yield	3.00%	3.00%
Repurchase Rate	0.15%	0.18%
Foreign currency exchange rate contracts | Minimum | Income Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Swap yield	(0.21%)	0.50%
Foreign currency exchange rate contracts | Maximum | Income Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Swap yield	3.09%	3.28%
Credit contracts | Minimum | Income Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Credit spreads	0.97%	0.97%
Credit contracts | Maximum | Income Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Credit spreads	0.98%	0.98%
Equity market contracts | Minimum | Income Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Correlation	70.00%	40.00%
Volatility	9.00%	12.00%
Equity market contracts | Maximum | Income Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Correlation	70.00%	40.00%
Volatility	33.00%	32.00%
Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Minimum | Income Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Utilization rates	0.00%	0.00%
Withdrawal rates	0.00%	0.00%
Long-term equity volatilities	9.10%	9.95%
Nonperformance risk spread	0.04%	0.04%
Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Minimum | Income Approach Valuation Technique | Durations 1 - 10
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Lapse Rate	0.25%	0.25%
Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Minimum | Income Approach Valuation Technique | Durations 11 - 20
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Lapse Rate	2.00%	2.00%
Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Minimum | Income Approach Valuation Technique | Durations 21 - 116
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Lapse Rate	1.25%	1.25%
Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Minimum | Income Approach Valuation Technique | Ages 0 - 40
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Mortality Rate	0.00%	0.00%
Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Minimum | Income Approach Valuation Technique | Ages 41 - 60
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Mortality Rate	0.01%	0.01%
Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Minimum | Income Approach Valuation Technique | Ages 61 - 115
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Mortality Rate	0.04%	0.04%
Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Maximum | Income Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Utilization rates	25.00%	25.00%
Withdrawal rates	20.00%	20.00%
Long-term equity volatilities	33.00%	33.00%
Nonperformance risk spread	1.64%	1.70%
Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Maximum | Income Approach Valuation Technique | Durations 1 - 10
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Lapse Rate	100.00%	100.00%
Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Maximum | Income Approach Valuation Technique | Durations 11 - 20
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Lapse Rate	100.00%	100.00%
Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Maximum | Income Approach Valuation Technique | Durations 21 - 116
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Lapse Rate	100.00%	100.00%
Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Maximum | Income Approach Valuation Technique | Ages 0 - 40
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Mortality Rate	0.21%	0.21%
Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Maximum | Income Approach Valuation Technique | Ages 41 - 60
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Mortality Rate	0.78%	0.78%
Embedded derivatives direct, assumed and ceded guaranteed minimum benefits | Maximum | Income Approach Valuation Technique | Ages 61 - 115
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Mortality Rate	100.00%	100.00%
U.S. corporate and foreign corporate securities | Minimum | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Delta spread adjustments	0.18%	0.18%
Offered quotes	$ 86	$ 37
Quoted prices	$ 13	$ 6
U.S. corporate and foreign corporate securities | Maximum | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Delta spread adjustments	1.44%	1.38%
Offered quotes	$ 119	$ 120
Quoted prices	$ 627	$ 700
U.S. corporate and foreign corporate securities | Weighted Average | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Delta spread adjustments	1.07%	1.05%
Offered quotes	$ 101	$ 99
Quoted prices	120	114
Foreign government | Minimum | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Quoted prices	41	98
Foreign government | Maximum | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Quoted prices	132	124
Foreign government | Weighted Average | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Quoted prices	110	104
RMBS | Minimum | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Quoted prices	19	19
RMBS | Maximum | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Quoted prices	163	137
RMBS | Weighted Average | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Quoted prices	92	91
ABS | Minimum | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Offered quotes	96	96
Quoted prices	5	5
ABS | Maximum | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Offered quotes	102	102
Quoted prices	106	106
ABS | Weighted Average | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Offered quotes	100	100
Quoted prices	$ 100	$ 99