Securities Available for Sale and Securities Held to Maturity (Securities with Unrealized Losses, Aggregated by Category and Period of Continuous Unrealized Loss) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013
Securities Available for Sale and Securities Held to Maturity [Abstract]
Securities available for sale Less than 12 months Fair Value	$ 5,626		$ 16,962
Securities available for sale Less than 12 months Unrealized Losses	13		200
Securities available for sale 12 months or longer Fair Value	7,071		1,856
Securities available for sale 12 months or longer Unrealized Losses	105		41
Total Securities available for sale with unrealized losses Total Fair Value	12,697		18,818
Total Securities available for sale with unrealized losses Total Unrealized Losses	118		241
Securities held to maturity Less than 12 months Fair Value	4,584		19,805
Securities held to maturity Less than 12 months Unrealized Losses	19		741
Securities held to maturity 12 months or longer Fair Value	12,210		2,605
Securities held to maturity 12 months or longer Unrealized Losses	369		248
Total Securities held to maturity with unrealized losses Total Fair Value	16,794		22,410
Total Securities held to maturity with unrealized losses Total Unrealized Losses	388		989
Securities Less than 12 months Fair Value	10,210	[1]	36,767	[2]
Securities Less than 12 months Unrealized Losses	32	[1]	941	[2]
Securities 12 months or longer Fair Value	19,281	[1]	4,461	[2]
Securities 12 months or longer Unrealized Losses	474	[1]	289	[2]
Total securities with unrealized losses Total Fair Value	29,491	[1]	41,228	[2]
Total securities with unrealized losses Total Unrealized Losses	$ 506	[1]	$ 1,230	[2]

[1] The number of investment positions with unrealized losses totaled 209 for securities available for sale and 144 for securities held to maturity.

[2] The number of investment positions with unrealized losses totaled 273 for securities available for sale and 193 for securities held to maturity.