Investment Securities - Schedule of Expected Maturities and Weighted Average Yields of Investment Securities by Major Security Type (Detail) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Securities available for sale
Due in 1 Year or Less	$ 1,043
Due 1 Year through 5 Years	25,884
Due 5 Years through 10 Years	12,563
Due 10 Years	602
Available-for-sale Securities	40,092	$ 39,061
Amortized cost of securities available for sale
Due in 1 Year or Less	1,048
Due 1 Year through 5 Years	25,625
Due 5 Years through 10 Years	12,295
Due 10 Years	571
Total Amortized Cost	$ 39,539	38,804
Weighted average yield for securities available for sale
Due in 1 Year or Less	1.03%
Due 1 Year through 5 Years	2.01%
Due 5 Years through 10 Years	3.19%
Due 10 Years	7.40%
Total weighted average yield	2.43%
Carrying value of securities held to maturity
Due in 1 Year or Less	$ 7
Due 1 Year through 5 Years	4,037
Due 5 Years through 10 Years	17,047
Due 10 Years	3,989
Carrying Value	25,080	24,619
Fair value of securities held to maturity
Due in 1 Year or Less	7
Due 1 Year through 5 Years	4,183
Due 5 Years through 10 Years	17,996
Due 10 Years	4,268
Fair Value	$ 26,454	25,317
Weighted average yield for securities held to maturity
Due in 1 Year or Less	7.13%
Due 1 Year through 5 Years	2.71%
Due 5 Years through 10 Years	2.57%
Due 10 Years	3.36%
Total weighted average yield	2.72%
U.S. Treasury securities
Carrying value of securities held to maturity
Due in 1 Year or Less	$ 0
Due 1 Year through 5 Years	199
Due 5 Years through 10 Years	0
Due 10 Years	0
Carrying Value	199	199
Fair value of securities held to maturity
Fair Value	200	198
U.S. Treasury securities
Securities available for sale
Due in 1 Year or Less	214
Due 1 Year through 5 Years	4,233
Due 5 Years through 10 Years	519
Due 10 Years	0
Available-for-sale Securities	4,966	4,660
Amortized cost of securities available for sale
Total Amortized Cost	4,934	4,664
RMBS
Securities available for sale
Due in 1 Year or Less	337
Due 1 Year through 5 Years	18,438
Due 5 Years through 10 Years	8,992
Due 10 Years	501
Available-for-sale Securities	28,268	27,311
Amortized cost of securities available for sale
Total Amortized Cost	27,800	27,012
RMBS \| Agency
Securities available for sale
Due in 1 Year or Less	323
Due 1 Year through 5 Years	17,587
Due 5 Years through 10 Years	7,457
Due 10 Years	0
Available-for-sale Securities	25,367	24,285
Amortized cost of securities available for sale
Total Amortized Cost	25,187	24,332
Carrying value of securities held to maturity
Due in 1 Year or Less	7
Due 1 Year through 5 Years	3,705
Due 5 Years through 10 Years	14,583
Due 10 Years	3,533
Carrying Value	21,828	21,513
Fair value of securities held to maturity
Fair Value	23,038	22,133
RMBS \| Non-Agency
Securities available for sale
Due in 1 Year or Less	14
Due 1 Year through 5 Years	851
Due 5 Years through 10 Years	1,535
Due 10 Years	501
Available-for-sale Securities	2,901	3,026
Amortized cost of securities available for sale
Total Amortized Cost	2,613	2,680
CMBS
Securities available for sale
Due in 1 Year or Less	172
Due 1 Year through 5 Years	2,362
Due 5 Years through 10 Years	2,970
Due 10 Years	0
Available-for-sale Securities	5,504	5,379
Amortized cost of securities available for sale
Total Amortized Cost	5,451	5,413
CMBS \| Agency
Securities available for sale
Due in 1 Year or Less	55
Due 1 Year through 5 Years	1,846
Due 5 Years through 10 Years	1,854
Due 10 Years	0
Available-for-sale Securities	3,755	3,664
Amortized cost of securities available for sale
Total Amortized Cost	3,732	3,690
Carrying value of securities held to maturity
Due in 1 Year or Less	0
Due 1 Year through 5 Years	133
Due 5 Years through 10 Years	2,464
Due 10 Years	456
Carrying Value	3,053	2,907
Fair value of securities held to maturity
Fair Value	3,216	2,986
CMBS \| Non-Agency
Securities available for sale
Due in 1 Year or Less	117
Due 1 Year through 5 Years	516
Due 5 Years through 10 Years	1,116
Due 10 Years	0
Available-for-sale Securities	1,749	1,715
Amortized cost of securities available for sale
Total Amortized Cost	1,719	1,723
Other ABS
Securities available for sale
Due in 1 Year or Less	110
Due 1 Year through 5 Years	846
Due 5 Years through 10 Years	82
Due 10 Years	0
Available-for-sale Securities	1,038	1,340
Amortized cost of securities available for sale
Total Amortized Cost	1,037	1,345
Other securities
Securities available for sale
Due in 1 Year or Less	210
Due 1 Year through 5 Years	5
Due 5 Years through 10 Years	0
Due 10 Years	101
Available-for-sale Securities	316	371
Amortized cost of securities available for sale
Total Amortized Cost	$ 317	$ 370

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

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

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