Loans Held for Investment portfolio and Related Allowance for Loan and Lease Losses (Detail) - USD ($) $ in Millions		Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Individually evaluated		$ 3,037	$ 3,068
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		246	255
Collectively evaluated		140,271	140,008
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		1,468	1,454
Total evaluated		143,308	143,076
Loans And Leases Receivable Allowance Loans Evaluated For Impairment Excluding Fair Value Loans		1,714	1,709
Loans Receivable, Fair Value Disclosure		221	222
Total	[1]	143,529	143,298
Loans and Leases Receivable, Allowance		1,714	1,709	$ 1,770	$ 1,752
Commercial Portfolio Segment [Member]
Individually evaluated		352	382
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		30	33
Collectively evaluated		77,901	77,842
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		1,090	1,091
Total evaluated		78,253	78,224
Loans And Leases Receivable Allowance Loans Evaluated For Impairment Excluding Fair Value Loans		1,120	1,124
Loans Receivable, Fair Value Disclosure		0	0
Total		78,253	78,224
Loans and Leases Receivable, Allowance		1,120	1,124	1,123	1,047
Residential Portfolio Segment [Member]
Individually evaluated		2,515	2,518
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		208	215
Collectively evaluated		35,814	36,250
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		146	154
Total evaluated		38,329	38,768
Loans And Leases Receivable Allowance Loans Evaluated For Impairment Excluding Fair Value Loans		354	369
Loans Receivable, Fair Value Disclosure		221	222
Total		38,550	38,990
Loans and Leases Receivable, Allowance		354	369	467	534
Consumer Portfolio Segment [Member]
Individually evaluated		170	168
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		8	7
Collectively evaluated		26,556	25,916
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		232	209
Total evaluated		26,726	26,084
Loans And Leases Receivable Allowance Loans Evaluated For Impairment Excluding Fair Value Loans		240	216
Loans Receivable, Fair Value Disclosure		0	0
Total		26,726	26,084
Loans and Leases Receivable, Allowance		$ 240	$ 216	$ 180	$ 171

[1] Includes loans of consolidated VIEs of $201 million and $211 million at March 31, 2017 and December 31, 2016, respectively.