Details of Holdings of Perpetual Securities (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Investment Holdings [Line Items]
Amortized Cost	$ 52,275	$ 55,951
Fair Value	54,036	55,890
Perpetual Securities
Investment Holdings [Line Items]
Amortized Cost	6,897	7,827
Fair Value	6,439	7,512
Unrealized Gain (Loss)	(458)	(315)
Perpetual Securities \| Upper Tier II
Investment Holdings [Line Items]
Amortized Cost	4,285	4,957
Fair Value	4,244	4,748
Unrealized Gain (Loss)	(41)	(209)
Perpetual Securities \| Upper Tier II \| AA
Investment Holdings [Line Items]
Amortized Cost	196	190
Fair Value	204	201
Unrealized Gain (Loss)	8	11
Perpetual Securities \| Upper Tier II \| A
Investment Holdings [Line Items]
Amortized Cost	2,108	3,279
Fair Value	2,046	3,250
Unrealized Gain (Loss)	(62)	(29)
Perpetual Securities \| Upper Tier II \| BBB
Investment Holdings [Line Items]
Amortized Cost	1,791	946
Fair Value	1,804	821
Unrealized Gain (Loss)	13	(125)
Perpetual Securities \| Upper Tier II \| BB or Lower
Investment Holdings [Line Items]
Amortized Cost	190	542
Fair Value	190	476
Unrealized Gain (Loss)	0	(66)
Perpetual Securities \| Tier I
Investment Holdings [Line Items]
Amortized Cost	2,268	2,542
Fair Value	1,834	2,421
Unrealized Gain (Loss)	(434)	(121)
Perpetual Securities \| Tier I \| A
Investment Holdings [Line Items]
Amortized Cost	0	632
Fair Value	0	568
Unrealized Gain (Loss)	0	(64)
Perpetual Securities \| Tier I \| BBB
Investment Holdings [Line Items]
Amortized Cost	1,684	1,386
Fair Value	1,417	1,296
Unrealized Gain (Loss)	(267)	(90)
Perpetual Securities \| Tier I \| BB or Lower
Investment Holdings [Line Items]
Amortized Cost	584	524
Fair Value	417	557
Unrealized Gain (Loss)	(167)	33
Perpetual Securities \| Other subordinated - non-banks \| BBB
Investment Holdings [Line Items]
Amortized Cost	344	328
Fair Value	361	343
Unrealized Gain (Loss)	$ 17	$ 15

For an unclassified balance sheet, this item represents investments in debt and equity securities which are categorized neither as held-to-maturity nor trading.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

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

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-Name Statement of Financial Accounting Standard (FAS)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 13

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 14

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 16

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 10: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-Section 25

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+ Details

- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References+ Details