Derivatives and Hedging Activities (Impact of Hedging Activity) (Details 5) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($) item	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) item	Sep. 30, 2014 USD ($)
Cash flow hedges [Member]
Derivative Instruments, Gain (Loss)
Estimated reclassification of net pretax losses on cash flow hedges from accumulated other comprehensive income to earnings during the next 12 months			$ 4
Cash flow hedge gain to be reclassified within twelve months to interest and debt expense			2
Cash flow hedge loss to be reclassified within twelve months recorded in net investment income			6
Amount of gain (loss) reclassified from accumulated other comprehensive income into income	$ (1)	$ (1)	$ (1)	$ (1)
Longest period of time over which the entity hedges exposure to the variability in future cash flows			20 years
Cash flow hedges [Member] | Interest and debt expense [Member]
Derivative Instruments, Gain (Loss)
Amount of gain (loss) reclassified from accumulated other comprehensive income into income	1	1	$ 3	3
Cash flow hedges [Member] | Net investment income [Member]
Derivative Instruments, Gain (Loss)
Amount of gain (loss) reclassified from accumulated other comprehensive income into income	$ (2)	(2)	$ (4)	(4)
Fair value hedges [Member]
Derivative Instruments, Gain (Loss)
Number of interest rate swaps held | item	3		3
Fair value hedges [Member] | Fixed rate debt [Member] | Interest and debt expense [Member]
Derivative Instruments, Gain (Loss)
Amount of gain recognized in income on derivatives	$ 8	$ 9	$ 24	$ 25