Loans Held for Investment portfolio and Related Allowance for Loan and Lease Losses (Detail) - USD ($) $ in Millions		Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015
Individually evaluated		$ 2,894		$ 3,068
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		226		255
Collectively evaluated		141,164		140,008
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		1,546		1,454
Total evaluated		144,058		143,076
Loans And Leases Receivable Allowance Loans Evaluated For Impairment Excluding Fair Value Loans		1,772		1,709
Loans Receivable, Fair Value Disclosure		206		222
Total	[1]	144,264		143,298
Loans and Leases Receivable, Allowance		1,772	$ 1,731	1,709	$ 1,743	$ 1,774	$ 1,752
Commercial Portfolio Segment [Member]
Individually evaluated		225		382
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		30		33
Collectively evaluated		76,735		77,842
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		1,093		1,091
Total evaluated		76,960		78,224
Loans And Leases Receivable Allowance Loans Evaluated For Impairment Excluding Fair Value Loans		1,123		1,124
Loans Receivable, Fair Value Disclosure		0		0
Total		76,960		78,224
Loans and Leases Receivable, Allowance		1,123	1,140	1,124	1,157	1,147	1,047
Residential Portfolio Segment [Member]
Individually evaluated		2,487		2,518
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		187		215
Collectively evaluated		36,037		36,250
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		164		154
Total evaluated		38,524		38,768
Loans And Leases Receivable Allowance Loans Evaluated For Impairment Excluding Fair Value Loans		351		369
Loans Receivable, Fair Value Disclosure		206		222
Total		38,730		38,990
Loans and Leases Receivable, Allowance		351	337	369	382	439	534
Consumer Portfolio Segment [Member]
Individually evaluated		182		168
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		9		7
Collectively evaluated		28,392		25,916
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		289		209
Total evaluated		28,574		26,084
Loans And Leases Receivable Allowance Loans Evaluated For Impairment Excluding Fair Value Loans		298		216
Loans Receivable, Fair Value Disclosure		0		0
Total		28,574		26,084
Loans and Leases Receivable, Allowance		$ 298	$ 254	$ 216	$ 204	$ 188	$ 171

[1] Includes loans of consolidated VIEs of $186 million and $211 million at September 30, 2017 and December 31, 2016, respectively.