Business Segments - Operating Results and Other Key Financial Measures (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Segment Reporting Information
Net interest income before provision for credit losses	$ 565,139	$ 599,861
Provision for credit losses	25,000	20,000
Noninterest income (loss)	78,988	59,978
Noninterest expense	246,875	218,447
INCOME BEFORE INCOME TAXES	372,252	421,392
Segment net income	285,075	322,439
Segment assets	70,875,670	67,244,898	$ 69,612,884
Consumer and Business Banking
Segment Reporting Information
Net interest income before provision for credit losses	291,764	304,242
Provision for credit losses	2,565	15,012
Noninterest income (loss)	25,542	26,002
Noninterest expense	119,300	113,823
INCOME BEFORE INCOME TAXES	195,441	201,409
Segment net income	137,672	142,247
Segment assets	19,629,076	17,880,525
Commercial Banking
Segment Reporting Information
Net interest income before provision for credit losses	260,349	236,723
Provision for credit losses	22,435	4,988
Noninterest income (loss)	46,466	43,599
Noninterest expense	106,307	87,248
INCOME BEFORE INCOME TAXES	178,073	188,086
Segment net income	125,581	134,457
Segment assets	35,049,899	33,647,465
Other
Segment Reporting Information
Net interest income before provision for credit losses	13,026	58,896
Provision for credit losses	0	0
Noninterest income (loss)	6,980	(9,623)
Noninterest expense	21,268	17,376
INCOME BEFORE INCOME TAXES	(1,262)	31,897
Segment net income	21,822	45,735
Segment assets	$ 16,196,695	$ 15,716,908