Investment Securities (Rollforward of Cumulative OTTI Credit Losses Recognized in Earnings) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Investment Securities Disclosure [Abstract]
Beginning balance	$ (1,160,000,000)	$ (1,201,000,000)
Loss where impairment was not previously recognized	(6,000,000)
Additional loss where credit impairment was previously recognized	(5,000,000)	(16,000,000)
Reduction due to credit impaired securities sold or matured	7,000,000	57,000,000
Ending balance	$ (1,164,000,000)	$ (1,160,000,000)