Securities Available for Sale and Securities Held to Maturity (Held To Maturity Securities with Unrealized Losses, Aggregated by Category and Period of Continuous Unrealized Loss) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013 security	Dec. 31, 2012 security
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity Less than 12 months Fair Value	$ 19,805	$ 2,920
Securities held to maturity Less than 12 months Unrealized Losses	741	20
Securities held to maturity 12 months or longer Fair Value	2,605
Securities held to maturity 12 months or longer Unrealized Losses	248
Total Securities held to maturity with unrealized losses Total Fair Value	22,410	2,920
Total Securities held to maturity with unrealized losses Total Unrealized Losses	989	20
Number of held to maturity securities in unrealized loss positions	193	24
U.S. agency mortgage-backed securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity Less than 12 months Fair Value	19,175	2,680
Securities held to maturity Less than 12 months Unrealized Losses	698	19
Securities held to maturity 12 months or longer Fair Value	2,345
Securities held to maturity 12 months or longer Unrealized Losses	223
Total Securities held to maturity with unrealized losses Total Fair Value	21,520	2,680
Total Securities held to maturity with unrealized losses Total Unrealized Losses	921	19
Non-agency commercial mortgage-backed securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity Less than 12 months Fair Value	630
Securities held to maturity Less than 12 months Unrealized Losses	43
Securities held to maturity 12 months or longer Fair Value	260
Securities held to maturity 12 months or longer Unrealized Losses	25
Total Securities held to maturity with unrealized losses Total Fair Value	890
Total Securities held to maturity with unrealized losses Total Unrealized Losses	68
Other securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity Less than 12 months Fair Value		240
Securities held to maturity Less than 12 months Unrealized Losses		1
Total Securities held to maturity with unrealized losses Total Fair Value		240
Total Securities held to maturity with unrealized losses Total Unrealized Losses		$ 1