Investment Securities - Schedule of Expected Maturities and Weighted Average Yields of Investment Securities by Major Security Type (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Securities available for sale
Due in 1 Year or Less	$ 1,647
Due 1 Year through 5 Years	22,246
Due 5 Years through 10 Years	14,572
Due 10 Years	596
Available-for-sale Securities	39,061	$ 39,508
Amortized cost of securities available for sale
Due in 1 Year or Less	1,651
Due 1 Year through 5 Years	22,169
Due 5 Years through 10 Years	14,444
Due 10 Years	540
Total Amortized Cost	$ 38,804	38,859
Weighted average yield for securities available for sale
Due in 1 Year or Less	0.80%
Due 1 Year through 5 Years	1.92%
Due 5 Years through 10 Years	3.01%
Due 10 Years	8.82%
Total weighted average yield	2.37%
Carrying value of securities held to maturity
Due in 1 Year or Less	$ 10
Due 1 Year through 5 Years	1,669
Due 5 Years through 10 Years	19,084
Due 10 Years	3,856
Carrying Value	24,619	22,500
Fair value of securities held to maturity
Due in 1 Year or Less	10
Due 1 Year through 5 Years	1,689
Due 5 Years through 10 Years	19,707
Due 10 Years	3,911
Fair Value	$ 25,317	23,634
Weighted average yield for securities held to maturity
Due in 1 Year or Less	5.73%
Due 1 Year through 5 Years	2.77%
Due 5 Years through 10 Years	2.48%
Due 10 Years	3.29%
Total weighted average yield	2.62%
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
Fair value of securities held to maturity
Fair Value	198
U.S. Treasury securities
Securities available for sale
Due in 1 Year or Less	701
Due 1 Year through 5 Years	3,958
Due 5 Years through 10 Years	1
Due 10 Years	0
Available-for-sale Securities	4,660	4,118
Amortized cost of securities available for sale
Total Amortized Cost	4,664	4,114
Corporate debt securities guaranteed by U.S. government agencies
Securities available for sale
Available-for-sale Securities		800
Amortized cost of securities available for sale
Total Amortized Cost		819
RMBS
Securities available for sale
Due in 1 Year or Less	256
Due 1 Year through 5 Years	14,741
Due 5 Years through 10 Years	11,840
Due 10 Years	474
Available-for-sale Securities	27,311	25,381
Amortized cost of securities available for sale
Total Amortized Cost	27,012	24,742
RMBS \| Agency
Securities available for sale
Due in 1 Year or Less	214
Due 1 Year through 5 Years	13,813
Due 5 Years through 10 Years	10,258
Due 10 Years	0
Available-for-sale Securities	24,285	21,995
Amortized cost of securities available for sale
Total Amortized Cost	24,332	21,804
Carrying value of securities held to maturity
Due in 1 Year or Less	10
Due 1 Year through 5 Years	1,336
Due 5 Years through 10 Years	16,697
Due 10 Years	3,470
Carrying Value	21,513	20,163
Fair value of securities held to maturity
Fair Value	22,133	21,210
RMBS \| Non-Agency
Securities available for sale
Due in 1 Year or Less	42
Due 1 Year through 5 Years	928
Due 5 Years through 10 Years	1,582
Due 10 Years	474
Available-for-sale Securities	3,026	3,386
Amortized cost of securities available for sale
Total Amortized Cost	2,680	2,938
CMBS
Securities available for sale
Due in 1 Year or Less	212
Due 1 Year through 5 Years	2,498
Due 5 Years through 10 Years	2,650
Due 10 Years	19
Available-for-sale Securities	5,379	5,519
Amortized cost of securities available for sale
Total Amortized Cost	5,413	5,531
CMBS \| Agency
Securities available for sale
Due in 1 Year or Less	48
Due 1 Year through 5 Years	2,042
Due 5 Years through 10 Years	1,555
Due 10 Years	19
Available-for-sale Securities	3,664	3,723
Amortized cost of securities available for sale
Total Amortized Cost	3,690	3,751
Carrying value of securities held to maturity
Due in 1 Year or Less	0
Due 1 Year through 5 Years	134
Due 5 Years through 10 Years	2,387
Due 10 Years	386
Carrying Value	2,907	2,337
Fair value of securities held to maturity
Fair Value	2,986	2,424
CMBS \| Non-Agency
Securities available for sale
Due in 1 Year or Less	164
Due 1 Year through 5 Years	456
Due 5 Years through 10 Years	1,095
Due 10 Years	0
Available-for-sale Securities	1,715	1,796
Amortized cost of securities available for sale
Total Amortized Cost	1,723	1,780
Other ABS
Securities available for sale
Due in 1 Year or Less	215
Due 1 Year through 5 Years	1,044
Due 5 Years through 10 Years	81
Due 10 Years	0
Available-for-sale Securities	1,340	2,662
Amortized cost of securities available for sale
Total Amortized Cost	1,345	2,618
Other securities
Securities available for sale
Due in 1 Year or Less	263
Due 1 Year through 5 Years	5
Due 5 Years through 10 Years	0
Due 10 Years	103
Available-for-sale Securities	371	1,028
Amortized cost of securities available for sale
Total Amortized Cost	$ 370	$ 1,035

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

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