Business Segments - Schedule of Financial Data for Business Segments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Average interest earning assets	$ 38,332,874	$ 37,767,710	$ 37,902,547	$ 36,743,806
Interest income	328,801	337,343	994,247	1,049,661
Interest expense	27,775	54,257	99,647	218,677
Net Interest Income	301,026	283,086	894,600	830,984
Provision (credit) for credit losses	3,531	30,908	20,934	106,747
Net Interest Income After Provision for Credit Losses	297,495	252,178	873,666	724,237
Non-interest income	42,431	49,272	116,790	135,499
Non-interest expense	174,922	160,185	507,028	473,007
Internal transfer expense (income)	0	0	0	0
Income Before Income Taxes	$ 165,004	$ 141,265	$ 483,428	$ 386,729
Return on average interest earning assets (pre-tax)	1.72%	1.50%	1.70%	1.40%
Consumer Lending
Segment Reporting Information [Line Items]
Return on average interest earning assets (pre-tax)			1.94%
Consumer Lending | Operating Segments
Segment Reporting Information [Line Items]
Average interest earning assets	$ 7,373,897	$ 7,126,157	$ 7,176,086	$ 7,187,839
Interest income	58,887	63,956	179,151	199,018
Interest expense	4,032	9,048	15,639	40,217
Net Interest Income	54,855	54,908	163,512	158,801
Provision (credit) for credit losses	(4,614)	5,383	(6,538)	15,274
Net Interest Income After Provision for Credit Losses	59,469	49,525	170,050	143,527
Non-interest income	11,845	23,531	47,445	55,383
Non-interest expense	13,520	19,877	53,161	60,188
Internal transfer expense (income)	20,662	18,614	60,026	58,355
Income Before Income Taxes	$ 37,132	$ 34,565	$ 104,308	$ 80,367
Return on average interest earning assets (pre-tax)	2.01%	1.94%		1.49%
Commercial Lending
Segment Reporting Information [Line Items]
Return on average interest earning assets (pre-tax)			2.16%
Commercial Lending | Operating Segments
Segment Reporting Information [Line Items]
Average interest earning assets	$ 25,324,485	$ 25,389,107	$ 25,465,276	$ 24,334,429
Interest income	250,866	251,920	759,097	771,947
Interest expense	13,795	33,330	55,497	136,156
Net Interest Income	237,071	218,590	703,600	635,791
Provision (credit) for credit losses	8,110	25,637	27,825	90,785
Net Interest Income After Provision for Credit Losses	228,961	192,953	675,775	545,006
Non-interest income	11,611	20,421	29,144	52,192
Non-interest expense	27,504	25,633	80,276	73,041
Internal transfer expense (income)	71,141	66,390	212,931	197,444
Income Before Income Taxes	$ 141,927	$ 121,351	$ 411,712	$ 326,713
Return on average interest earning assets (pre-tax)	2.24%	1.91%		1.79%
Investment Management
Segment Reporting Information [Line Items]
Return on average interest earning assets (pre-tax)			0.23%
Investment Management | Operating Segments
Segment Reporting Information [Line Items]
Average interest earning assets	$ 5,634,492	$ 5,252,446	$ 5,261,185	$ 5,221,538
Interest income	19,766	22,513	58,514	81,905
Interest expense	3,228	6,728	11,466	29,216
Net Interest Income	16,538	15,785	47,048	52,689
Provision (credit) for credit losses	35	(112)	(353)	688
Net Interest Income After Provision for Credit Losses	16,503	15,897	47,401	52,001
Non-interest income	2,018	(1,304)	6,824	7,661
Non-interest expense	(150)	(186)	1,370	843
Internal transfer expense (income)	15,825	13,713	43,706	42,393
Income Before Income Taxes	$ 2,846	$ 1,066	9,149	$ 16,426
Return on average interest earning assets (pre-tax)	0.20%	0.08%		0.42%
Corporate and Other Adjustments | Corporate and Other Adjustments
Segment Reporting Information [Line Items]
Average interest earning assets	$ 0	$ 0	0	$ 0
Interest income	(718)	(1,046)	(2,515)	(3,209)
Interest expense	6,720	5,151	17,045	13,088
Net Interest Income	(7,438)	(6,197)	(19,560)	(16,297)
Provision (credit) for credit losses	0	0	0	0
Net Interest Income After Provision for Credit Losses	(7,438)	(6,197)	(19,560)	(16,297)
Non-interest income	16,957	6,624	33,377	20,263
Non-interest expense	134,048	114,861	372,221	338,935
Internal transfer expense (income)	(107,628)	(98,717)	(316,663)	(298,192)
Income Before Income Taxes	$ (16,901)	$ (15,717)	$ (41,741)	$ (36,777)