Loans Held for Investment portfolio and Related Allowance for Loan and Lease Losses (Detail) - USD ($) $ in Millions	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Individually evaluated	$ 2,210		$ 2,611
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	165		167
Collectively evaluated	154,252		149,065
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	1,516		1,448
Total evaluated	156,462		151,676
Loans And Leases Receivable Allowance Loans Evaluated For Impairment Excluding Fair Value Loans	1,681		1,615
Loans Receivable, Fair Value Disclosure	127		163
Total	156,589		151,839
Loans and Leases Receivable, Allowance	1,681	$ 1,643	1,615	$ 1,650	$ 1,694	$ 1,735
Commercial Portfolio Segment [Member]
Individually evaluated	302		149
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	49		13
Collectively evaluated	83,689		80,791
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	1,153		1,067
Total evaluated	83,991		80,940
Loans And Leases Receivable Allowance Loans Evaluated For Impairment Excluding Fair Value Loans	1,202		1,080
Loans Receivable, Fair Value Disclosure	0		0
Total	83,991		80,940
Loans and Leases Receivable, Allowance	1,202	1,136	1,080	1,068	1,068	1,101
Residential Portfolio Segment [Member]
Total	38,300		38,900
Consumer Portfolio Segment [Member]
Individually evaluated	1,908		2,462
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	116		154
Collectively evaluated	70,563		68,274
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	363		381
Total evaluated	72,471		70,736
Loans And Leases Receivable Allowance Loans Evaluated For Impairment Excluding Fair Value Loans	479		535
Total	72,598		70,899
Loans and Leases Receivable, Allowance	$ 479	$ 507	$ 535	$ 582	$ 626	$ 634