Fair Value (Quantitative Information) (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
U.S. corporate and foreign corporate securities [Member] | Minimum [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Delta spread adjustments	(0.50%)	(0.50%)
Illiquidity premium	0.30%	0.30%
Offered quotes	$ 18	$ 0
Matrix Pricing - Offered quotes	$ 0	$ 0
Credit spreads	(14.24%)	(14.16%)
U.S. corporate and foreign corporate securities [Member] | Maximum [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Delta spread adjustments	2.50%	5.00%
Illiquidity premium	0.30%	0.30%
Offered quotes	$ 575	$ 555
Matrix Pricing - Offered quotes	$ 127	$ 348
Credit spreads	7.16%	8.76%
U.S. corporate and foreign corporate securities [Member] | Weighted Average [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Delta spread adjustments	0.86%	0.90%
Illiquidity premium	0.30%	0.30%
Offered quotes	$ 94	$ 92
Matrix Pricing - Offered quotes	$ 100	$ 115
Credit spreads	2.59%	2.72%
Foreign government debt securities [Member] | Minimum [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Offered quotes	$ 82	$ 82
Quoted prices	$ 0	$ 77
Credit spreads	0.05%	(0.58%)
Foreign government debt securities [Member] | Maximum [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Offered quotes	$ 187	$ 200
Quoted prices	$ 149	$ 146
Credit spreads	0.52%	1.50%
Foreign government debt securities [Member] | Weighted Average [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Offered quotes	$ 120	$ 117
Quoted prices	$ 93	$ 99
Credit spreads	0.31%	0.72%
RMBS [Member] | Minimum [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Offered quotes	$ 22	$ 28
Quoted prices	$ 73	$ 13
Credit spreads	(1.23%)	0.09%
RMBS [Member] | Maximum [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Offered quotes	$ 100	$ 100
Quoted prices	$ 110	$ 109
Credit spreads	29.80%	29.80%
RMBS [Member] | Weighted Average [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Offered quotes	$ 75	$ 75
Quoted prices	$ 97	$ 100
Credit spreads	3.42%	5.21%
CMBS [Member] | Minimum [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Offered quotes	$ 109
Quoted prices	$ 11	$ 1
Credit spreads	3.83%	0.01%
CMBS [Member] | Maximum [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Offered quotes	$ 109
Quoted prices	$ 104	$ 106
Credit spreads	148.11%	91.64%
CMBS [Member] | Weighted Average [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Offered quotes	$ 109
Quoted prices	$ 98	$ 99
Credit spreads	8.74%	3.74%
ABS [Member] | Minimum [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Offered quotes	$ 0	$ 0
Quoted prices	$ 0	$ 40
Credit spreads	0.35%	0.00%
ABS [Member] | Maximum [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Offered quotes	$ 111	$ 111
Quoted prices	$ 109	$ 105
Credit spreads	18.28%	18.29%
ABS [Member] | Weighted Average [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Offered quotes	$ 90	$ 97
Quoted prices	$ 101	$ 100
Credit spreads	1.83%	1.09%
Interest rate contracts [Member] | Minimum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Swap yield	1.86%	1.86%
Interest rate contracts [Member] | Maximum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Swap yield	3.78%	3.53%
Foreign currency contracts [Member] | Minimum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Swap yield	2.30%	2.28%
Correlation	43.00%	43.00%
Foreign currency contracts [Member] | Maximum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Swap yield	7.62%	7.95%
Correlation	58.00%	57.00%
Credit contracts [Member] | Minimum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Credit spreads	1.00%	1.00%
Credit contracts [Member] | Maximum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Credit spreads	1.00%	1.00%
Equity market contracts [Member] | Minimum [Member] | Present Value techniques or option pricing model [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Correlation	60.00%	65.00%
Volatility	14.00%	13.00%
Equity market contracts [Member] | Maximum [Member] | Present Value techniques or option pricing model [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Correlation	60.00%	65.00%
Volatility	29.00%	32.00%
Embedded derivatives direct and assumed guaranteed benefits [Member] | Minimum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Utilization rates	20.00%	20.00%
Withdrawal rates	0.00%	0.07%
Long-term equity volatilities	13.69%	15.18%
Nonperformance risk spread	(0.08%)	0.10%
Embedded derivatives direct and assumed guaranteed benefits [Member] | Minimum [Member] | Income Approach Valuation Technique [Member] | Durations 1-10 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Lapse rates	0.50%	0.50%
Embedded derivatives direct and assumed guaranteed benefits [Member] | Minimum [Member] | Income Approach Valuation Technique [Member] | Durations 11-20 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Lapse rates	2.00%	2.00%
Embedded derivatives direct and assumed guaranteed benefits [Member] | Minimum [Member] | Income Approach Valuation Technique [Member] | Durations 21-116 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Lapse rates	2.00%	2.00%
Embedded derivatives direct and assumed guaranteed benefits [Member] | Minimum [Member] | Income Approach Valuation Technique [Member] | Ages 0-40 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Mortality rates	0.00%	0.00%
Embedded derivatives direct and assumed guaranteed benefits [Member] | Minimum [Member] | Income Approach Valuation Technique [Member] | Ages 41-60 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Mortality rates	0.05%	0.05%
Embedded derivatives direct and assumed guaranteed benefits [Member] | Minimum [Member] | Income Approach Valuation Technique [Member] | Ages 61-115 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Mortality rates	0.26%	0.26%
Embedded derivatives direct and assumed guaranteed benefits [Member] | Maximum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Utilization rates	50.00%	50.00%
Withdrawal rates	20.00%	20.00%
Long-term equity volatilities	40.00%	40.00%
Nonperformance risk spread	1.42%	1.72%
Embedded derivatives direct and assumed guaranteed benefits [Member] | Maximum [Member] | Income Approach Valuation Technique [Member] | Durations 1-10 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Lapse rates	100.00%	100.00%
Embedded derivatives direct and assumed guaranteed benefits [Member] | Maximum [Member] | Income Approach Valuation Technique [Member] | Durations 11-20 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Lapse rates	100.00%	100.00%
Embedded derivatives direct and assumed guaranteed benefits [Member] | Maximum [Member] | Income Approach Valuation Technique [Member] | Durations 21-116 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Lapse rates	100.00%	100.00%
Embedded derivatives direct and assumed guaranteed benefits [Member] | Maximum [Member] | Income Approach Valuation Technique [Member] | Ages 0-40 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Mortality rates	0.14%	0.14%
Embedded derivatives direct and assumed guaranteed benefits [Member] | Maximum [Member] | Income Approach Valuation Technique [Member] | Ages 41-60 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Mortality rates	0.88%	0.88%
Embedded derivatives direct and assumed guaranteed benefits [Member] | Maximum [Member] | Income Approach Valuation Technique [Member] | Ages 61-115 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Mortality rates	100.00%	100.00%