Loans Held for Investment portfolio and Related Allowance for Loan and Lease Losses (Detail) - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Individually evaluated		$ 2,821	$ 3,068
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		204	255
Collectively evaluated		140,164	140,008
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		1,531	1,454
Total evaluated		142,985	143,076
Loans And Leases Receivable Allowance Loans Evaluated For Impairment Excluding Fair Value Loans		1,735	1,709
Loans Receivable, Fair Value Disclosure		196	222
Total	[1]	143,181	143,298
Loans and Leases Receivable, Allowance		1,735	1,709	$ 1,752
Commercial Portfolio Segment [Member]
Individually evaluated		173	382
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		21	33
Collectively evaluated		75,304	77,842
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		1,080	1,091
Total evaluated		75,477	78,224
Loans And Leases Receivable Allowance Loans Evaluated For Impairment Excluding Fair Value Loans		1,101	1,124
Loans Receivable, Fair Value Disclosure		0	0
Total		75,477	78,224
Loans and Leases Receivable, Allowance		1,101	1,124	1,047
Residential Portfolio Segment [Member]
Total		38,620	38,990
Consumer Portfolio Segment [Member]
Individually evaluated		2,648	2,686
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		183	222
Collectively evaluated		64,860	62,166
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		451	363
Total evaluated		67,508	64,852
Loans And Leases Receivable Allowance Loans Evaluated For Impairment Excluding Fair Value Loans		634	585
Loans Receivable, Fair Value Disclosure		196	222
Total		67,704	65,074
Loans and Leases Receivable, Allowance		$ 634	$ 585	$ 705

[1] Includes loans of consolidated VIEs of $179 million and $211 million at December 31, 2017 and December 31, 2016, respectively.