Segment Reporting (Operating Results and Total Assets Reportable Segments) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Segment Reporting Information [Line Items]
Goodwill	$ 2,868,068		$ 2,631,465	$ 2,514,104
Assets	76,161,693		74,945,249
Net interest income	567,739	$ 595,283
Non-interest income	99,353	70,766
Non-interest expense	335,923	332,467
Pre-tax, pre-provision net revenue	331,169	333,582
Provision (benefit) for credit losses	45,500	46,749
Income before income taxes	285,669	286,833
Income tax expense	69,346	65,829
Net income	216,323	221,004
Operating Segments | Commercial Banking
Segment Reporting Information [Line Items]
Goodwill	1,960,363		1,951,945
Assets	42,286,247		41,843,297
Net interest income	341,942	360,293
Non-interest income	34,280	33,720
Non-interest expense	106,225	98,833
Pre-tax, pre-provision net revenue	269,997	295,180
Provision (benefit) for credit losses	47,283	35,250
Income before income taxes	222,714	259,930
Income tax expense	49,220	57,964
Net income	173,494	201,966
Operating Segments | Healthcare Financial Services
Segment Reporting Information [Line Items]
Goodwill	285,670		57,485
Assets	509,012		122,421
Net interest income	86,138	71,730
Non-interest income	31,061	24,067
Non-interest expense	52,127	43,700
Pre-tax, pre-provision net revenue	65,072	52,097
Provision (benefit) for credit losses	0	0
Income before income taxes	65,072	52,097
Income tax expense	17,114	14,066
Net income	47,958	38,031
Operating Segments | Consumer Banking
Segment Reporting Information [Line Items]
Goodwill	622,035		622,035
Assets	12,268,347		12,327,403
Net interest income	205,777	234,604
Non-interest income	33,978	27,636
Non-interest expense	120,121	116,555
Pre-tax, pre-provision net revenue	119,634	145,685
Provision (benefit) for credit losses	(4,089)	2,571
Income before income taxes	123,723	143,114
Income tax expense	30,436	35,922
Net income	93,287	107,192
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Goodwill	0		0
Assets	21,098,087		$ 20,652,128
Net interest income	(66,118)	(71,344)
Non-interest income	34	(14,657)
Non-interest expense	57,450	73,379
Pre-tax, pre-provision net revenue	(123,534)	(159,380)
Provision (benefit) for credit losses	2,306	8,928
Income before income taxes	(125,840)	(168,308)
Income tax expense	(27,424)	(42,123)
Net income	$ (98,416)	$ (126,185)