Loans and Allowance for Credit Losses - Schedule of Composition of Loans and Impact of Adoption (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2021
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	$ 32,577,834		$ 31,123,641
Allowance for credit losses on loans	(303,982)	$ (300,555)	(303,671)	$ (302,254)	$ (288,003)	$ (107,341)
Net loans	32,273,852		30,819,970
Portfolio Segment Reclassifications
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0		0
After Reclassifications
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	32,577,834		31,123,641
Allowance for credit losses on loans	(303,982)		(303,671)
Net loans	32,273,852		30,819,970
Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	9,333,448		9,508,904
Allowance for credit losses on loans	(124,755)	(127,403)	(120,612)	(112,413)	(102,819)	(27,232)
Commercial | Portfolio Segment Reclassifications
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	(226,353)		(210,280)
Commercial | After Reclassifications
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	9,107,095		9,298,624
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	13,916,221		12,457,070
Allowance for credit losses on loans	(144,975)	(136,897)	(138,244)	(144,090)	(141,802)	(64,004)
Commercial real estate | Portfolio Segment Reclassifications
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	(165,593)		(158,322)
Commercial real estate | After Reclassifications
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	13,750,628		12,298,748
BBCC
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses on loans	(2,709)	(2,776)	(2,431)	(2,168)	(2,064)	(2,458)
BBCC | Portfolio Segment Reclassifications
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	391,946		368,602
BBCC | After Reclassifications
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	391,946		368,602
Residential real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	6,696,288		6,460,441
Allowance for credit losses on loans	(20,780)	(20,421)	(21,916)	(21,256)	(19,729)	(9,347)
Residential real estate | Portfolio Segment Reclassifications
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0		0
Residential real estate | After Reclassifications
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	6,696,288		6,460,441
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	2,631,877		2,697,226
Consumer | Portfolio Segment Reclassifications
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	(2,631,877)		(2,697,226)
Indirect
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1,047,224		1,034,257
Allowance for credit losses on loans	(1,321)	(1,407)	(1,532)	(1,585)	(1,641)	(1,743)
Indirect | Portfolio Segment Reclassifications
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1,047,224		1,034,257
Indirect | After Reclassifications
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1,047,224		1,034,257
Direct
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	542,689		629,186
Allowance for credit losses on loans	(3,571)	(4,755)	(12,116)	(16,096)	(14,412)	(528)
Direct | Portfolio Segment Reclassifications
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	542,689		629,186
Direct | After Reclassifications
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	542,689		629,186
Home equity
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1,041,964		1,033,783
Allowance for credit losses on loans	(5,871)	$ (6,896)	(6,820)	$ (4,646)	$ (5,536)	$ (2,029)
Home equity | Portfolio Segment Reclassifications
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1,041,964		1,033,783
Home equity | After Reclassifications
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1,041,964		1,033,783
Direct Finance Leases
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	$ 173,000		$ 188,100