Operating Segments - Schedule of Financial Data for Business Segments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Segment Reporting Information [Line Items]
Average interest earning assets	$ 56,802,565	$ 50,531,242	$ 56,510,997	$ 46,605,417
Interest income	813,018	536,728	2,320,707	1,330,133
Interest expense	400,600	82,736	1,052,504	140,312
Net interest income	412,418	453,992	1,268,203	1,189,821
(Credit) provision for credit losses	9,117	2,023	29,604	49,578
Net interest income after provision for credit losses	403,301	451,969	1,238,599	1,140,243
Non-interest income	58,664	56,194	173,038	153,997
Non-interest expense	267,133	261,639	822,270	758,709
Internal transfer expense (income)	0	0	0	0
Income (loss) before income taxes	$ 194,832	$ 246,524	$ 589,367	$ 535,531
Return on average interest earning assets (pre-tax)	1.37%	1.95%	1.39%	1.53%
Consumer Banking | Operating Segments
Segment Reporting Information [Line Items]
Average interest earning assets	$ 8,941,112	$ 8,307,993	$ 8,871,992	$ 7,978,732
Interest income	94,280	70,590	270,198	193,186
Interest expense	60,950	12,288	159,154	20,218
Net interest income	33,330	58,302	111,044	172,968
(Credit) provision for credit losses	(4,568)	7,182	5,368	14,457
Net interest income after provision for credit losses	37,898	51,120	105,676	158,511
Non-interest income	22,591	19,637	62,410	50,540
Non-interest expense	19,944	24,352	61,416	59,711
Internal transfer expense (income)	28,273	26,268	81,174	92,544
Income (loss) before income taxes	$ 12,272	$ 20,137	$ 25,496	$ 56,796
Return on average interest earning assets (pre-tax)	0.55%	0.97%	0.38%	0.95%
Commercial Banking | Operating Segments
Segment Reporting Information [Line Items]
Average interest earning assets	$ 41,078,302	$ 36,033,901	$ 40,248,161	$ 32,551,062
Interest income	659,360	425,930	1,853,839	1,036,276
Interest expense	279,415	53,294	722,009	84,356
Net interest income	379,945	372,636	1,131,830	951,920
(Credit) provision for credit losses	13,715	(5,347)	19,561	34,590
Net interest income after provision for credit losses	366,230	377,983	1,112,269	917,330
Non-interest income	11,208	23,510	41,316	54,815
Non-interest expense	33,141	31,759	104,229	81,292
Internal transfer expense (income)	127,249	113,932	361,239	371,213
Income (loss) before income taxes	$ 217,048	$ 255,802	$ 688,117	$ 519,640
Return on average interest earning assets (pre-tax)	2.11%	2.84%	2.28%	2.13%
Treasury and Corporate Other | Operating Segments
Segment Reporting Information [Line Items]
Average interest earning assets				$ 6,075,623
Interest income				100,671
Interest expense				35,738
Net interest income				64,933
(Credit) provision for credit losses				531
Net interest income after provision for credit losses				64,402
Non-interest income				48,642
Non-interest expense				617,706
Internal transfer expense (income)				(463,757)
Income (loss) before income taxes				$ (40,905)
Return on average interest earning assets (pre-tax)				(0.90%)
Treasury and Corporate Other | Treasury and Corporate Other
Segment Reporting Information [Line Items]
Average interest earning assets	$ 6,783,151	$ 6,189,348	$ 7,390,844
Interest income	59,378	40,208	196,670
Interest expense	60,235	17,154	171,341
Net interest income	(857)	23,054	25,329
(Credit) provision for credit losses	(30)	188	4,675
Net interest income after provision for credit losses	(827)	22,866	20,654
Non-interest income	24,865	13,047	69,312
Non-interest expense	214,048	205,528	656,625
Internal transfer expense (income)	(155,522)	(140,200)	(442,413)
Income (loss) before income taxes	$ (34,488)	$ (29,415)	$ (124,246)
Return on average interest earning assets (pre-tax)	(2.03%)	(1.90%)	(2.24%)