Fair Value (Quantitative Information) (Details) - $ / shares	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Interest rate contracts | Minimum | Income Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Swap yield	2.72%	3.07%
Interest rate contracts | Maximum | Income Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Swap yield	3.97%	3.17%
Foreign currency exchange rate contracts | Minimum | Income Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Swap yield	0.85%	0.28%
Correlation	0.00%	0.00%
Foreign currency exchange rate contracts | Maximum | Income Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Swap yield	3.42%	3.81%
Correlation	0.00%	0.00%
Credit contracts | Minimum | Income Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Credit spreads	0.97%	0.98%
Credit contracts | Maximum | Income Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Credit spreads	1.00%	1.00%
Equity market contracts | Minimum | Income Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Correlation	70.00%	70.00%
Volatility	12.00%	15.00%
Equity market contracts | Maximum | Income Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Correlation	70.00%	70.00%
Volatility	35.00%	36.00%
Embedded derivatives direct and assumed 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	8.85%	8.79%
Nonperformance risk spread	(0.14%)	(0.47%)
Embedded derivatives direct and assumed 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 and assumed 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 and assumed guaranteed minimum benefits | Minimum | Income Approach Valuation Technique | Durations 21 - 116
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Lapse Rate	2.50%	1.00%
Embedded derivatives direct and assumed 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 and assumed 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 and assumed 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 and assumed 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	1.42%	1.31%
Embedded derivatives direct and assumed 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 and assumed 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 and assumed 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 and assumed 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 and assumed guaranteed minimum benefits | Maximum | Income Approach Valuation Technique | Ages 41 - 60
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Mortality Rate	0.73%	0.78%
Embedded derivatives direct and assumed 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	(3.13%)	(0.65%)
Offered quotes	$ 68	$ 68
Quoted prices	$ 0	$ 0
U.S. corporate and foreign corporate securities | Maximum | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Delta spread adjustments	4.70%	2.40%
Offered quotes	$ 121	$ 121
Quoted prices	$ 780	$ 780
U.S. corporate and foreign corporate securities | Weighted Average | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Delta spread adjustments	(0.29%)	0.39%
Offered quotes	$ 98	$ 98
Quoted prices	157	156
Foreign government | Minimum | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Quoted prices	94	96
Foreign government | Maximum | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Quoted prices	135	135
Foreign government | Weighted Average | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Quoted prices	105	113
RMBS | Minimum | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Quoted prices	5	19
RMBS | Maximum | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Quoted prices	604	292
RMBS | Weighted Average | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Quoted prices	93	92
ABS | Minimum | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Offered quotes	92	66
Quoted prices	5	16
ABS | Maximum | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Offered quotes	107	105
Quoted prices	112	109
ABS | Weighted Average | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Offered quotes	100	99
Quoted prices	$ 101	$ 100