Business Segments (Operating Results and Other Key Financial Measures) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Segment Reporting Information
Net interest income (loss) before provision for credit losses	$ 415,613	$ 353,695
Provision for credit losses	8,000	0
Noninterest income	79,743	72,866
Noninterest expense	189,450	191,077
Segment income (loss) before income taxes	297,906	235,484
Segment net income	237,652	204,994
Segment assets	62,241,456	56,874,146	$ 60,870,701
Consumer and Business Banking
Segment Reporting Information
Net interest income (loss) before provision for credit losses	213,214	149,899
Provision for credit losses	3,104	(4,249)
Noninterest income	25,199	23,442
Noninterest expense	96,095	89,286
Segment income (loss) before income taxes	139,214	88,304
Segment net income	99,164	63,251
Segment assets	15,338,579	14,147,094
Commercial Banking
Segment Reporting Information
Net interest income (loss) before provision for credit losses	208,077	177,092
Provision for credit losses	4,896	4,249
Noninterest income	49,077	47,396
Noninterest expense	73,395	69,257
Segment income (loss) before income taxes	178,863	150,982
Segment net income	127,507	108,207
Segment assets	30,199,416	27,222,272
Other
Segment Reporting Information
Net interest income (loss) before provision for credit losses	(5,678)	26,704
Provision for credit losses	0	0
Noninterest income	5,467	2,028
Noninterest expense	19,960	32,534
Segment income (loss) before income taxes	(20,171)	(3,802)
Segment net income	10,981	33,536
Segment assets	$ 16,703,461	$ 15,504,780