Securities (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Securities available for sale
Securities available-for-sale, Debt, Amortized Cost	$ 20,240	$ 22,626
Securities available-for-sale, Gross Unrealized Gains	347	277
Securities available-for-sale, Gross Unrealized Losses	42	70
Total securities available-for-sale, Fair Value	20,545	22,833
U.S. government sponsored agencies [Member]
Securities available for sale
Securities available-for-sale, Debt, Amortized Cost	5,393	6,943
Securities available-for-sale, Gross Unrealized Gains	66	54
Securities available-for-sale, Gross Unrealized Losses	0
Total securities available-for-sale, Fair Value	5,459	6,997
U.S. government and government sponsored agencies [Member]
Securities available for sale
Securities available-for-sale, Debt, Amortized Cost	11,125	13,307
Securities available-for-sale, Gross Unrealized Gains	213	182
Securities available-for-sale, Gross Unrealized Losses	1	4
Total securities available-for-sale, Fair Value	11,337	13,485
Privately issued [Member]
Securities available for sale
Securities available-for-sale, Debt, Amortized Cost	653	800
Securities available-for-sale, Gross Unrealized Gains	4	1
Securities available-for-sale, Gross Unrealized Losses	34	63
Total securities available-for-sale, Fair Value	623	738
Commercial mortgage-backed securities [Member]
Securities available for sale
Securities available-for-sale, Debt, Amortized Cost	1,503	1,032
Securities available-for-sale, Gross Unrealized Gains	53	29
Securities available-for-sale, Gross Unrealized Losses	2	1
Total securities available-for-sale, Fair Value	1,554	1,060
Other debt securities [Member]
Securities available for sale
Securities available-for-sale, Debt, Amortized Cost	1,480	463
Securities available-for-sale, Gross Unrealized Gains	11	11
Securities available-for-sale, Gross Unrealized Losses	5	2
Total securities available-for-sale, Fair Value	1,486	472
Equity securities [Member]
Securities available for sale
Securities available-for-sale, Equity, Amortized Cost	86	81
Total securities available-for-sale, Fair Value	$ 86	$ 81

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

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This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

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