Business Segments - Operating Results and Other Key Financial Measures (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Segment Reporting Information
Net interest income (loss) before provision for credit losses	$ 472,952	$ 376,473	$ 888,565	$ 730,168
Provision for (reversal of) credit losses	13,500	(15,000)	21,500	(15,000)
Noninterest income	78,444	68,431	158,187	141,297
Noninterest expense	196,860	189,523	386,310	380,600
Segment income (loss) before income taxes	341,036	270,381	638,942	505,865
Segment net income (loss)	258,329	224,742	495,981	429,736
Segment assets	62,394,283	59,854,876	62,394,283	59,854,876	$ 60,870,701
Consumer and Business Banking
Segment Reporting Information
Net interest income (loss) before provision for credit losses	284,373	173,775	497,587	323,674
Provision for (reversal of) credit losses	2,898	2,358	6,002	(1,891)
Noninterest income	28,384	24,332	53,583	47,774
Noninterest expense	94,295	87,650	190,390	176,936
Segment income (loss) before income taxes	215,564	108,099	354,778	196,403
Segment net income (loss)	153,549	77,429	252,713	140,680
Segment assets	16,472,373	14,594,087	16,472,373	14,594,087
Commercial Banking
Segment Reporting Information
Net interest income (loss) before provision for credit losses	230,964	192,696	439,041	369,788
Provision for (reversal of) credit losses	10,602	(17,358)	15,498	(13,109)
Noninterest income	48,032	32,674	97,109	80,070
Noninterest expense	81,023	64,164	154,418	133,421
Segment income (loss) before income taxes	187,371	178,564	366,234	329,546
Segment net income (loss)	133,861	127,873	261,368	236,080
Segment assets	32,256,044	27,354,253	32,256,044	27,354,253
Other
Segment Reporting Information
Net interest income (loss) before provision for credit losses	(42,385)	10,002	(48,063)	36,706
Provision for (reversal of) credit losses	0	0	0	0
Noninterest income	2,028	11,425	7,495	13,453
Noninterest expense	21,542	37,709	41,502	70,243
Segment income (loss) before income taxes	(61,899)	(16,282)	(82,070)	(20,084)
Segment net income (loss)	(29,081)	19,440	(18,100)	52,976
Segment assets	$ 13,665,866	$ 17,906,536	$ 13,665,866	$ 17,906,536