Reinsurance - Guaranteed Minimum Death Benefits Account Value, Amount at Risk, and Contractholders (Details) (Variable Annuity [Member], Guaranteed Minimum Death Benefit [Member], USD $) In Billions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2013 Contractholders	Dec. 31, 2012 Contractholders
Variable Annuity [Member] | Guaranteed Minimum Death Benefit [Member]
Guaranteed Minimum Death Benefits Account Value Risk And Average Age Table [Line Items]
Aggregate value of underlying mutual fund investments, GMDB contracts	$ 13.7	$ 13.3
Death benefit coverage in force, GMDB contracts	$ 3.2	$ 4.0
Total contractholders, GMDB contracts	400,000	435,000