Derivatives (Estimated Fair Value of Derivative Assets and Liabilities after Master Netting Agreements and Cash Collateral) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 10,434	$ 13,777
Derivative Liability, Fair Value	4,945	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	10,647	14,067
Derivative Liability, Fair Value	4,978	5,650
Estimated fair value of derivative assets presented in the consolidated balance sheets	10,647	14,067
Estimated fair value of derivative liabilities presented in the consolidated balance sheets	4,978	5,650
Net amount of derivative assets after application of master netting agreements and cash collateral	364	0
Net amount of derivative liabilities after application of master netting agreements and cash collateral	148	42
Netting [Member] \| Over the Counter [Member]
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Gross Asset	10,620	14,048
Derivative Liability, Fair Value	4,908	5,480
Gross estimated fair value of derivative assets	(4,147)	(4,562)
Gross estimated fair value of derivative liabilities	(4,147)	(4,562)
Cash collateral on derivative assets	(3,099)	(5,960)
Cash collateral on derivative liabilities	(2)	(1)
Securities collateral on derivative assets	(3,012)	(3,526)
Securities collateral on derivative liabilities	(611)	(875)
Netting [Member] \| Exchange Traded [Member]
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Gross Asset	22	19
Derivative Liability, Fair Value	69	170
Gross estimated fair value of derivative assets	(20)	(19)
Gross estimated fair value of derivative liabilities	(20)	(19)
Cash collateral on derivative assets	0	0
Cash collateral on derivative liabilities	(49)	(151)
Securities collateral on derivative assets	0	0
Securities collateral on derivative liabilities	0	0
Netting [Member] \| Cleared [Member]
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Gross Asset	5	0
Derivative Liability, Fair Value	1	0
Gross estimated fair value of derivative assets	0	0
Gross estimated fair value of derivative liabilities	0	0
Cash collateral on derivative assets	(5)	0
Cash collateral on derivative liabilities	(1)	0
Securities collateral on derivative assets	0	0
Securities collateral on derivative liabilities	$ 0	$ 0

Amount of obligation to return cash collateral under master netting arrangements offset against derivative assets.

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Amount of obligation to return securities collateral under master netting arrangements offset against derivative assets.

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Fair value of financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, not subject to a master netting arrangement.

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Amount of right to receive cash collateral under master netting arrangements offset against derivative liabilities.

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Amount of right to receive securities collateral under master netting arrangements offset against derivative liabilities.

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Fair value of financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, not subject to a master netting arrangement.

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No definition available.

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Fair values as of the balance sheet date of all assets resulting from contracts that meet the criteria of being accounted for as derivative instruments, net of the effects of master netting arrangements.

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Fair value of derivative asset, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.

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The amount as of the balance sheet date of the fair value of derivative assets that in accordance with the entity's accounting policy was not offset against an obligation to return cash collateral under a master netting arrangement.

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The amount as of the balance sheet date of the fair value of derivative assets that in accordance with the entity's accounting policy was offset against an obligation to return cash collateral under a master netting arrangement.

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Fair value of derivative liability, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.

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The amount as of the balance sheet date of the fair value of derivative liabilities that in accordance with the entity's accounting policy was not offset against the right to reclaim cash collateral under a master netting arrangement.

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The amount as of the balance sheet date of the fair value of derivative liabilities that in accordance with the entity's accounting policy were offset against the right to reclaim cash collateral under a master netting arrangement.

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Fair values as of the balance sheet date of all liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments, net of the effects of master netting arrangements.

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