Segment Information - Information about Company's Segments (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Net interest income	$ 7,115	$ 5,822	$ 3,825
Noninterest income	2,528	2,357	2,167
Total income	9,643	8,179	5,992
Provision for credit losses	645	517	(75)
Amortization of core deposit and other intangible assets	62	56	10
Depreciation and other amortization	435	379	314
Other noninterest expense	4,882	4,615	3,288
Income (loss) before taxes	3,619	2,612	2,455
Income tax expense (benefit)	878	620	596
Net income (loss)	2,741	1,992	1,859
Average total assets	205,397	190,252	152,669
Capital expenditures	256	214	149
All Other [Member]
Segment Reporting Information [Line Items]
Net interest income	(346)	109	182
Noninterest income	103	59	61
Total income	(243)	168	243
Provision for credit losses	175	351	(313)
Amortization of core deposit and other intangible assets	62	56	9
Depreciation and other amortization	139	134	114
Other noninterest expense	508	662	264
Income (loss) before taxes	(1,127)	(1,035)	169
Income tax expense (benefit)	(371)	(344)	(5)
Net income (loss)	(756)	(691)	174
Average total assets	70,266	67,635	52,095
Capital expenditures	144	88	79
Commercial Banking [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net interest income	2,409	2,302	1,558
Noninterest income	658	588	509
Total income	3,067	2,890	2,067
Provision for credit losses	297	66	169
Amortization of core deposit and other intangible assets			1
Depreciation and other amortization	39	39	39
Other noninterest expense	1,307	1,085	748
Income (loss) before taxes	1,424	1,700	1,110
Income tax expense (benefit)	385	458	297
Net income (loss)	1,039	1,242	813
Average total assets	80,243	69,960	53,578
Capital expenditures	2	2	3
Retail Banking [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net interest income	4,352	3,008	1,929
Noninterest income	762	703	831
Total income	5,114	3,711	2,760
Provision for credit losses	173	101	69
Depreciation and other amortization	249	198	152
Other noninterest expense	2,208	2,009	1,508
Income (loss) before taxes	2,484	1,403	1,031
Income tax expense (benefit)	646	364	266
Net income (loss)	1,838	1,039	765
Average total assets	51,213	49,059	43,736
Capital expenditures	104	122	55
Institutional Services and Wealth Management [ Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net interest income	700	403	156
Noninterest income	1,005	1,007	766
Total income	1,705	1,410	922
Provision for credit losses		(1)
Depreciation and other amortization	8	8	9
Other noninterest expense	859	859	768
Income (loss) before taxes	838	544	145
Income tax expense (benefit)	218	142	38
Net income (loss)	620	402	107
Average total assets	3,675	3,598	3,260
Capital expenditures	$ 6	$ 2	$ 12