Securities (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011
SECURITIES AVAILABLE FOR SALE
Amortized Cost	$ 14,128	$ 15,490	$ 19,082
Gross Unrealized Gains	505	522	406
Gross Unrealized Losses			40
Fair Value	14,633	16,012	19,448
HELD-TO-MATURITY SECURITIES
Held-to-maturity securities	3,019	2,109	19
Held-to-maturity Securities, Unrecognized Holding Gains	33	24
Held-to-maturity Securities, Unrecognized Holding Losses	0
Fair Value	3,052	2,133	19
U.S. Treasury, agencies and corporations [Member]
SECURITIES AVAILABLE FOR SALE
Amortized Cost			9
Fair Value			9
States and political subdivisions [Member]
SECURITIES AVAILABLE FOR SALE
Amortized Cost	59	60	148
Gross Unrealized Gains	3	3	2
Fair Value	62	63	150
HELD-TO-MATURITY SECURITIES
Held-to-maturity securities			1
Fair Value			1
Collateralized mortgage obligations [Member]
SECURITIES AVAILABLE FOR SALE
Amortized Cost	13,405	14,707	17,998
Gross Unrealized Gains	440	455	331
Gross Unrealized Losses			40
Fair Value	13,845	15,162	18,289
HELD-TO-MATURITY SECURITIES
Held-to-maturity securities	3,001	2,091
Held-to-maturity Securities, Unrecognized Holding Gains	33	24
Held-to-maturity Securities, Unrecognized Holding Losses	0
Fair Value	3,034	2,115
Other mortgage-backed securities [Member]
SECURITIES AVAILABLE FOR SALE
Amortized Cost	653	715	913
Gross Unrealized Gains	61	63	68
Fair Value	714	778	981
Other securities [Member]
SECURITIES AVAILABLE FOR SALE
Amortized Cost	11	8	14
Gross Unrealized Gains	1	1	5
Fair Value	12	9	19
HELD-TO-MATURITY SECURITIES
Held-to-maturity securities	18	18	18
Held-to-maturity Securities, Unrecognized Holding Losses	0
Fair Value	$ 18	$ 18	$ 18

For an unclassified balance sheet, this item represents investments in debt and equity securities which are categorized neither as held-to-maturity nor trading. Such securities are reported at fair value, with unrealized gains and losses excluded from earnings and reported in a separate component of shareholders' equity (other comprehensive income), unless the Available-for-sale Security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding gain or loss of an Available-for-sale Security that is designated as being hedged in a fair value hedge shall be recognized in earnings during the period of the hedge, as should other than temporary declines in fair value below costs basis.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 16

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 22

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 12

-Subparagraph b

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 13

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 14

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments made for accretion, amortization, other-than-temporary impairments, and hedging, if any.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 7

-Footnote 2

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

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This item represents the gross unrealized gains for securities which are categorized neither as held-to-maturity nor trading securities. Such gross unrealized gains are the excess of the fair value of the Available-for-sale Securities over their carrying value as of the reporting date. Such gross unrealized gains are included in other comprehensive income in the statement of shareholders' equity, unless the Available-for-sale Security is designated as a hedge. All or a portion of the unrealized holding gain of an available-for-sale security that is designated as being hedged in a fair value hedge shall be recognized in earnings during the period of the hedge.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 22

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 13, 19

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This item represents the gross unrealized losses for securities which are categorized neither as held-to-maturity nor trading securities. Such gross unrealized losses are the excess of the carrying value of the Available-for-sale Securities over their fair value as of the reporting date. Such gross unrealized losses are included in other comprehensive income in the statement of shareholders' equity, unless the Available-for-sale Security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding loss of an Available-for-sale Security that is designated as being hedged in a fair value hedge shall be recognized in earnings during the period of the hedge, as should other than temporary declines in fair value below costs basis.

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For an unclassified balance sheet, this item represents investments in debt securities which are categorized as held-to-maturity; such investments are measured at amortized cost (carrying value). The held-to-maturity category is for those securities that the Entity has the positive intent and ability to hold until maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

-Number 43

-Chapter 3

-Section A

-Paragraph 4, 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 17

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 7, 8, 9, 10, 11

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This item represents the aggregate fair value of investments in debt securities as of the balance sheet date and which are categorized as held-to-maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 19

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 137

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As of the balance sheet date, the excess of fair value over carrying value (amortized cost) of a debt security categorized as held-to-maturity, exclusive of dividend or interest income recognized but not yet received and exclusive of any write-downs for other-than-temporary impairment. Such item represents the gross unrecognized holding gain.

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As of the balance sheet date, the excess of carrying value (amortized cost) over fair value of a debt security categorized as held-to-maturity, exclusive of dividend or interest income recognized but not yet received and exclusive of any write-downs for other-than-temporary impairment. Such item represents the gross unrecognized holding loss.

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