Investment Securities - Schedule of Expected Maturities and Weighted Average Yields of Investment Securities by Major Security Type (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Securities available for sale
Due in 1 Year or Less	$ 2,350
Due 1 Year through 5 Years	20,137
Due 5 Years through 10 Years	16,316
Due 10 Years	862
Securities available for sale	39,665	41,800
Amortized cost of securities available for sale
Due in 1 Year or Less	2,349
Due 1 Year through 5 Years	19,945
Due 5 Years through 10 Years	16,065
Due 10 Years	744
Total Amortized Cost	39,103	41,632
Weighted average yield for securities available for sale
Due in 1 Year or Less	1.16%
Due 1 Year through 5 Years	2.14%
Due 5 Years through 10 Years	3.01%
Due 10 Years	7.90%
Total weighted average yield	2.55%
Carrying value of securities held to maturity
Due in 1 Year or Less	0
Due 1 Year through 5 Years	618
Due 5 Years through 10 Years	18,760
Due 10 Years	2,804
Carrying Value	22,182	19,132
Fair value of securities held to maturity
Due in 1 Year or Less	0
Due 1 Year through 5 Years	616
Due 5 Years through 10 Years	19,348
Due 10 Years	2,964
Fair Value	22,928	19,185
Weighted average yield for securities held to maturity
Due in 1 Year or Less	0.00%
Due 1 Year through 5 Years	2.38%
Due 5 Years through 10 Years	2.70%
Due 10 Years	3.32%
Total weighted average yield	2.76%
U.S. Treasury debt obligations
Securities available for sale
Due in 1 Year or Less	653
Due 1 Year through 5 Years	3,608
Due 5 Years through 10 Years	0
Due 10 Years	0
Securities available for sale	4,261	833
Amortized cost of securities available for sale
Total Amortized Cost	4,261	831
U.S. agency debt obligations
Securities available for sale
Due in 1 Year or Less	1
Due 1 Year through 5 Years	0
Due 5 Years through 10 Years	0
Due 10 Years	0
Securities available for sale	1	1
Amortized cost of securities available for sale
Total Amortized Cost	1	1
Corporate debt securities guaranteed by U.S. government agencies
Securities available for sale
Due in 1 Year or Less	0
Due 1 Year through 5 Years	392
Due 5 Years through 10 Years	573
Due 10 Years	14
Securities available for sale	979	1,234
Amortized cost of securities available for sale
Total Amortized Cost	1,001	1,282
RMBS
Securities available for sale
Due in 1 Year or Less	175
Due 1 Year through 5 Years	10,942
Due 5 Years through 10 Years	12,728
Due 10 Years	638
Securities available for sale	24,483	25,079
Amortized cost of securities available for sale
Total Amortized Cost	23,877	24,737
RMBS \| Agency
Securities available for sale
Due in 1 Year or Less	158
Due 1 Year through 5 Years	9,998
Due 5 Years through 10 Years	10,830
Due 10 Years	0
Securities available for sale	20,986	21,479
Amortized cost of securities available for sale
Total Amortized Cost	20,853	21,572
Carrying value of securities held to maturity
Due in 1 Year or Less	0
Due 1 Year through 5 Years	193
Due 5 Years through 10 Years	17,421
Due 10 Years	2,735
Carrying Value	20,349	17,443
Fair value of securities held to maturity
Fair Value	21,038	17,485
RMBS \| Non-Agency
Securities available for sale
Due in 1 Year or Less	17
Due 1 Year through 5 Years	944
Due 5 Years through 10 Years	1,898
Due 10 Years	638
Securities available for sale	3,497	3,600
Amortized cost of securities available for sale
Total Amortized Cost	3,024	3,165
CMBS
Securities available for sale
Due in 1 Year or Less	447
Due 1 Year through 5 Years	3,174
Due 5 Years through 10 Years	2,145
Due 10 Years	20
Securities available for sale	5,786	6,006
Amortized cost of securities available for sale
Total Amortized Cost	5,838	6,116
CMBS \| Agency
Securities available for sale
Due in 1 Year or Less	364
Due 1 Year through 5 Years	2,672
Due 5 Years through 10 Years	947
Due 10 Years	0
Securities available for sale	3,983	4,198
Amortized cost of securities available for sale
Total Amortized Cost	4,029	4,262
Carrying value of securities held to maturity
Due in 1 Year or Less	0
Due 1 Year through 5 Years	425
Due 5 Years through 10 Years	1,339
Due 10 Years	69
Carrying Value	1,833	1,689
Fair value of securities held to maturity
Fair Value	1,890	1,700
CMBS \| Non-Agency
Securities available for sale
Due in 1 Year or Less	83
Due 1 Year through 5 Years	502
Due 5 Years through 10 Years	1,198
Due 10 Years	20
Securities available for sale	1,803	1,808
Amortized cost of securities available for sale
Total Amortized Cost	1,809	1,854
Other ABS
Securities available for sale
Due in 1 Year or Less	1,019
Due 1 Year through 5 Years	1,705
Due 5 Years through 10 Years	256
Due 10 Years	103
Securities available for sale	3,083	7,136
Amortized cost of securities available for sale
Total Amortized Cost	3,038	7,123
Other securities
Securities available for sale
Due in 1 Year or Less	55
Due 1 Year through 5 Years	316
Due 5 Years through 10 Years	614
Due 10 Years	87
Securities available for sale	1,072	1,511
Amortized cost of securities available for sale
Total Amortized Cost	$ 1,087	$ 1,542

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Available-for-sale Securities, Expected Debt Maturities, Next Rolling Twelve Months, Amortized Cost Basis

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Available-for-sale Securities, Expected Debt Maturities, Next Rolling Twelve Months, Fair Value

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Available-for-sale Securities, Expected Debt Maturities, Next Rolling Twelve Months, Weighted Average Yield

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Available-for-sale Securities, Expected Debt Maturities, Rolling after Year Ten, Amortized Cost Basis

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Available-for-sale Securities, Expected Debt Maturities, Rolling after Year Ten, Fair Value

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Available-for-sale Securities, Expected Debt Maturities, Rolling after Year Ten, Weighted Average Yield

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Available-for-sale Securities, Expected Debt Maturities, Rolling Year Six Through Ten, Amortized Cost Basis

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Available-for-sale Securities, Expected Debt Maturities, Rolling Year Six Through Ten, Fair Value

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Available-for-sale Securities, Expected Debt Maturities, Rolling Year Six Through Ten, Weighted Average Yield

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Available-for-sale Securities, Expected Debt Maturities, Rolling Year Two Through Five, Amortized Cost Basis

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Available-for-sale Securities, Expected Debt Maturities, Rolling Year Two Through Five, Fair Value

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Available-for-sale Securities, Expected Debt Maturities, Rolling Year Two Through Five, Weighted Average Yield

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Available-for-sale Securities, Weighted Average Yield

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Held-to-maturity Securities, Expected Debt Maturities, after Five Through Ten Years, Net Carrying Amount

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No definition available.

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Held-to-maturity Securities, Expected Debt Maturities, after One Through Five Years, Net Carrying Amount

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Held-to-maturity Securities, Expected Debt Maturities, after Ten Years, Net Carrying Amount

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No definition available.

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Held-to-maturity Securities, Expected Debt Maturities, Next Rolling Twelve Months, Fair Value

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Held-to-maturity Securities, Expected Debt Maturities, Next Rolling Twelve Months, Weighted-Average Yield

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Held-to-maturity Securities, Expected Debt Maturities, Rolling after Ten Years, Fair Value

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No definition available.

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Held-to-maturity Securities, Expected Debt Maturities, Rolling after Ten Years, Weighted-Average Yield

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Held-to-maturity Securities, Expected Debt Maturities, Rolling Year Six Through Ten, Fair Value

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Held-to-maturity Securities, Expected Debt Maturities, Rolling Year Six Through Ten, Weighted-Average Yield

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Held-to-maturity Securities, Expected Debt Maturities, Rolling Year Two Through Five, Fair Value

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Held-to-maturity Securities, Expected Debt Maturities, Rolling Year Two Through Five, Weighted-Average Yield

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Held to maturity securities expected debt maturities weighted average yield

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Held-to-maturity Securities, Expected Debt Maturities, within One Year, Net Carrying Amount

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

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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 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.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.2)

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Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 5

-Subparagraph (f)

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-Name Accounting Standards Codification

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-Name Accounting Standards Codification

-Topic 944

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Fair value of investments in debt securities classified as held-to-maturity.

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