Fair Value Measurements - Guaranteed Minimum Income Benefit Contracts Liabilities (Details) (Derivative Financial Instruments, Liabilities [Member], Variable Annuity [Member], Guaranteed Minimum Income Benefit [Member])	9 Months Ended
	Sep. 30, 2013
Maximum [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Nonperformance risk adjustment, entity	1.35%
Minimum [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Nonperformance risk adjustment, entity	0.05%
Weighted Average [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Nonperformance risk adjustment, entity	0.50%