Derivatives (Estimated Fair Value of Derivative Assets and Liabilities after Master Netting Agreements and Cash Collateral) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 8,595	$ 13,777
Derivative Liability, Fair Value, Gross Liability	6,521	5,536
Amounts offset in the consolidated balance sheet, Assets	0	0
Amounts offset in the consolidated balance sheet, Liabilities	0	0
Netting [Member]
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Gross Asset	8,850	14,067
Derivative Liability, Fair Value, Gross Liability	6,549	5,650
Estimated fair value of derivative assets presented in the consolidated balance sheets	8,850	14,067
Estimated fair value of derivative liabilities presented in the consolidated balance sheets	6,549	5,650
Net amount of derivative assets after application of master netting agreements and cash collateral	139	0
Net amount of derivative liabilities after application of master netting agreements and cash collateral	269	42
Netting [Member] | Over the Counter [Member]
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Gross Asset	8,537	14,048
Derivative Liability, Fair Value, Gross Liability	6,367	5,480
Gross estimated fair value of derivative assets	(4,631)	(4,562)
Gross estimated fair value of derivative liabilities	(4,631)	(4,562)
Cash collateral on derivative assets	(1,679)	(5,960)
Cash collateral on derivative liabilities	(3)	(1)
Securities collateral on derivative assets	(2,105)	(3,526)
Securities collateral on derivative liabilities	(1,464)	(875)
Netting [Member] | Exchange Traded [Member]
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Gross Asset	11	19
Derivative Liability, Fair Value, Gross Liability	53	170
Gross estimated fair value of derivative assets	(5)	(19)
Gross estimated fair value of derivative liabilities	(5)	(19)
Cash collateral on derivative assets	0	0
Cash collateral on derivative liabilities	(44)	(151)
Securities collateral on derivative assets	0	0
Securities collateral on derivative liabilities	(4)	0
Netting [Member] | Cleared [Member]
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Gross Asset	302	0
Derivative Liability, Fair Value, Gross Liability	129	0
Gross estimated fair value of derivative assets	(122)	0
Gross estimated fair value of derivative liabilities	(122)	0
Cash collateral on derivative assets	(169)	0
Cash collateral on derivative liabilities	(7)	0
Securities collateral on derivative assets	0	0
Securities collateral on derivative liabilities	$ 0	$ 0