Loans Held for Investment portfolio and Related Allowance for Loan and Lease Losses (Detail) - USD ($) $ in Millions		Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016
Individually evaluated		$ 2,822		$ 2,821
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		197		204
Collectively evaluated		141,936		140,164
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		1,453		1,531
Total evaluated		144,758		142,985
Loans And Leases Receivable Allowance Loans Evaluated For Impairment Excluding Fair Value Loans		1,650		1,735
Loans Receivable, Fair Value Disclosure		177		196
Total	[1]	144,935		143,181
Loans and Leases Receivable, Allowance		1,650	$ 1,694	1,735	$ 1,731	$ 1,714	$ 1,709
Commercial Portfolio Segment [Member]
Individually evaluated		256		173
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		26		21
Collectively evaluated		76,845		75,304
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		1,042		1,080
Total evaluated		77,101		75,477
Loans And Leases Receivable Allowance Loans Evaluated For Impairment Excluding Fair Value Loans		1,068		1,101
Loans Receivable, Fair Value Disclosure		0		0
Total		77,101		75,477
Loans and Leases Receivable, Allowance		1,068	1,068	1,101	1,140	1,120	1,124
Residential Portfolio Segment [Member]
Total		38,216		38,620
Consumer Portfolio Segment [Member]
Individually evaluated		2,566		2,648
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		171		183
Collectively evaluated		65,091		64,860
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		411		451
Total evaluated		67,657		67,508
Loans And Leases Receivable Allowance Loans Evaluated For Impairment Excluding Fair Value Loans		582		634
Loans Receivable, Fair Value Disclosure		177		196
Total		67,834		67,704
Loans and Leases Receivable, Allowance		$ 582	$ 626	$ 634	$ 591	$ 594	$ 585

[1] Includes loans of consolidated VIEs of $165 million and $179 million at June 30, 2018 and December 31, 2017, respectively.