Derivatives (Level 3 Derivative Instruments) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Equity Index Options
Quantitative information for Level 3 Fair Value Measurements Liabilities
Fair value Liabilities	63.7
Equity Index Options | Black-Scholes option pricing model | Minimum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Adjustment to counterparty valuations	(1.10%)
Equity Index Options | Black-Scholes option pricing model | Maximum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Adjustment to counterparty valuations	(2.50%)
Equity Index Options | Black-Scholes option pricing model | Weighted Average
Quantitative information for Level 3 Fair Value Measurements Liabilities
Adjustment to counterparty valuations	(1.50%)
Variable annuity benefit guarantee liabilities
Quantitative information for Level 3 Fair Value Measurements Liabilities
Fair value Liabilities	441.5
Variable annuity benefit guarantee liabilities | Discounted cash flows | Minimum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Surrenders
Mortality	0.00%
Foreign exchange volatilities
Index volatilities
Variable annuity benefit guarantee liabilities | Discounted cash flows | Maximum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Surrenders
Mortality	4.80%
Foreign exchange volatilities
Index volatilities
Variable annuity benefit guarantee liabilities | Discounted cash flows | Weighted Average
Quantitative information for Level 3 Fair Value Measurements Liabilities
Surrenders
Mortality	0.90%
Foreign exchange volatilities
Index volatilities
Foreign Exchange Options
Quantitative information for Level 3 Fair Value Measurements Liabilities
Fair value Liabilities	76.8
Foreign Exchange Options | Black-Scholes option pricing model | Minimum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Foreign exchange volatilities	(2.20%)
Foreign Exchange Options | Black-Scholes option pricing model | Maximum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Foreign exchange volatilities	(7.90%)
Foreign Exchange Options | Black-Scholes option pricing model | Weighted Average
Quantitative information for Level 3 Fair Value Measurements Liabilities
Foreign exchange volatilities	(3.40%)
Year One | Variable annuity benefit guarantee liabilities | Discounted cash flows | Minimum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Surrenders	0.30%
Foreign exchange volatilities	11.30%
Index volatilities	13.60%
Year One | Variable annuity benefit guarantee liabilities | Discounted cash flows | Maximum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Surrenders	3.00%
Foreign exchange volatilities	12.50%
Index volatilities	19.30%
Year One | Variable annuity benefit guarantee liabilities | Discounted cash flows | Weighted Average
Quantitative information for Level 3 Fair Value Measurements Liabilities
Surrenders	0.50%
Foreign exchange volatilities	12.20%
Index volatilities	14.50%
Year Two | Variable annuity benefit guarantee liabilities | Discounted cash flows | Minimum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Surrenders	0.20%
Foreign exchange volatilities	10.70%
Index volatilities	17.50%
Year Two | Variable annuity benefit guarantee liabilities | Discounted cash flows | Maximum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Surrenders	3.00%
Foreign exchange volatilities	13.20%
Index volatilities	22.70%
Year Two | Variable annuity benefit guarantee liabilities | Discounted cash flows | Weighted Average
Quantitative information for Level 3 Fair Value Measurements Liabilities
Surrenders	0.40%
Foreign exchange volatilities	12.10%
Index volatilities	19.20%
Year Three and Thereafter | Variable annuity benefit guarantee liabilities | Discounted cash flows | Minimum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Surrenders	0.10%
Foreign exchange volatilities	10.00%
Index volatilities	19.90%
Year Three and Thereafter | Variable annuity benefit guarantee liabilities | Discounted cash flows | Maximum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Surrenders	3.00%
Foreign exchange volatilities	15.40%
Index volatilities	22.70%
Year Three and Thereafter | Variable annuity benefit guarantee liabilities | Discounted cash flows | Weighted Average
Quantitative information for Level 3 Fair Value Measurements Liabilities
Surrenders	0.40%
Foreign exchange volatilities	13.10%
Index volatilities	21.80%