Allowance for Credit Losses - Schedule of Activity in the Allowance for Credit Losses by Loan Portfolio (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2022
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses at beginning of period	$ 437,069	$ 387,380	$ 427,265	$ 357,448
Other adjustments	30	(60)	(20)	(15)
Charge-offs	(31,018)	(10,477)	(89,615)	(36,344)
Recoveries	4,283	2,359	11,144	5,731
Provision for credit losses - Other	6,799		68,389
Provision for credit losses - Day 1 on non-PCD assets acquired during the period	15,547		15,547
Provision for credit losses	22,300	19,948	83,900	71,589
Initial allowance for credit losses recognized on PCD assets acquired during the period	3,004		3,004
Allowance for credit losses at period end	435,714	399,150	435,714	399,150	$ 357,448
Accounting Standards Update [Extensible Enumeration]					Accounting Standards Update 2022-02 [Member]
Individually measured	27,630	15,302	27,630	15,302
Collectively measured	408,084	383,848	408,084	383,848
Loans at period end, individually evaluated for impairment	124,586	77,937	124,586	77,937
Loans at period end, collectively evaluated for impairment	46,804,823	41,196,917	46,804,823	41,196,917
Loans held-for-investment	138,038	171,178	138,038	$ 171,178
Accounting Standards Update 2016-13
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Accounting Standards Update [Extensible Enumeration]				Accounting Standards Update 2016-13
Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses at beginning of period				$ 741
Allowance for credit losses at period end					$ 741
Commercial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses at beginning of period	181,991	143,142	169,604	142,769
Other adjustments	0	0	0	0
Charge-offs	(22,975)	(2,427)	(43,774)	(10,599)
Recoveries	649	1,162	2,078	2,059
Provision for credit losses - Other	7,128		38,885
Provision for credit losses - Day 1 on non-PCD assets acquired during the period	2,967		2,967
Provision for credit losses		9,611		17,148
Initial allowance for credit losses recognized on PCD assets acquired during the period	1,838		1,838
Allowance for credit losses at period end	171,598	151,488	171,598	151,488	142,769
Individually measured	21,573	9,773	21,573	9,773
Collectively measured	150,025	141,715	150,025	141,715
Loans at period end, individually evaluated for impairment	63,826	43,569	63,826	43,569
Loans at period end, collectively evaluated for impairment	15,183,867	12,681,904	15,183,867	12,681,904
Loans held-for-investment	0	0	0	0
Commercial | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses at beginning of period				111
Allowance for credit losses at period end					111
Commercial Real Estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses at beginning of period	223,728	215,696	223,853	184,352
Other adjustments	0	0	0	0
Charge-offs	(95)	(1,713)	(21,090)	(9,842)
Recoveries	30	243	151	368
Provision for credit losses - Other	(4,162)		16,587
Provision for credit losses - Day 1 on non-PCD assets acquired during the period	10,540		10,540
Provision for credit losses		1,492		39,484
Initial allowance for credit losses recognized on PCD assets acquired during the period	1,103		1,103
Allowance for credit losses at period end	231,144	215,718	231,144	215,718	184,352
Individually measured	5,958	5,408	5,958	5,408
Collectively measured	225,186	210,310	225,186	210,310
Loans at period end, individually evaluated for impairment	42,071	17,043	42,071	17,043
Loans at period end, collectively evaluated for impairment	12,751,346	10,929,137	12,751,346	10,929,137
Loans held-for-investment	0	0	0	0
Commercial Real Estate | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses at beginning of period				1,356
Allowance for credit losses at period end					1,356
Home  Equity
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses at beginning of period	7,242	6,967	7,116	7,573
Other adjustments	0	0	0	0
Charge-offs	0	(227)	(74)	(227)
Recoveries	101	33	165	105
Provision for credit losses - Other	134		270
Provision for credit losses - Day 1 on non-PCD assets acquired during the period	1,344		1,344
Provision for credit losses		307		(338)
Initial allowance for credit losses recognized on PCD assets acquired during the period	2		2
Allowance for credit losses at period end	8,823	7,080	8,823	7,080	7,573
Individually measured	50	0	50	0
Collectively measured	8,773	7,080	8,773	7,080
Loans at period end, individually evaluated for impairment	1,122	1,363	1,122	1,363
Loans at period end, collectively evaluated for impairment	425,921	341,895	425,921	341,895
Loans held-for-investment	0	0	0	0
Home  Equity | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses at beginning of period				(33)
Allowance for credit losses at period end					(33)
Residential real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses at beginning of period	8,773	12,252	13,133	11,585
Other adjustments	0	0	0	0
Charge-offs	0	(78)	(61)	(78)
Recoveries	5	1	15	11
Provision for credit losses - Other	268		(4,041)
Provision for credit losses - Day 1 on non-PCD assets acquired during the period	638		638
Provision for credit losses		484		1,833
Initial allowance for credit losses recognized on PCD assets acquired during the period	61		61
Allowance for credit losses at period end	9,745	12,659	9,745	12,659	11,585
Individually measured	48	109	48	109
Collectively measured	9,697	12,550	9,697	12,550
Loans at period end, individually evaluated for impairment	17,565	15,946	17,565	15,946
Loans at period end, collectively evaluated for impairment	3,232,435	2,520,479	3,232,435	2,520,479
Loans held-for-investment	138,038	171,178	138,038	171,178
Residential real estate | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses at beginning of period				(692)
Allowance for credit losses at period end					(692)
Premium Finance Receivables
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses at beginning of period	14,746	9,046	13,069	10,671
Other adjustments	30	(60)	(20)	(15)
Charge-offs	(7,794)	(5,848)	(24,218)	(15,151)
Recoveries	3,477	906	8,667	3,119
Provision for credit losses - Other	3,284		16,245
Provision for credit losses - Day 1 on non-PCD assets acquired during the period	0		0
Provision for credit losses		7,776		13,196
Initial allowance for credit losses recognized on PCD assets acquired during the period	0		0
Allowance for credit losses at period end	13,743	11,820	13,743	11,820	10,671
Individually measured	0	0	0	0
Collectively measured	13,743	11,820	13,743	11,820
Loans at period end, individually evaluated for impairment	0	0	0	0
Loans at period end, collectively evaluated for impairment	15,128,580	14,654,555	15,128,580	14,654,555
Loans held-for-investment	0	0	0	0
Premium Finance Receivables | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses at beginning of period				0
Allowance for credit losses at period end					0
Consumer and Other
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses at beginning of period	589	277	490	498
Other adjustments	0	0	0	0
Charge-offs	(154)	(184)	(398)	(447)
Recoveries	21	14	68	69
Provision for credit losses - Other	147		443
Provision for credit losses - Day 1 on non-PCD assets acquired during the period	58		58
Provision for credit losses		278		266
Initial allowance for credit losses recognized on PCD assets acquired during the period	0		0
Allowance for credit losses at period end	661	385	661	385	498
Individually measured	1	12	1	12
Collectively measured	660	373	660	373
Loans at period end, individually evaluated for impairment	2	16	2	16
Loans at period end, collectively evaluated for impairment	82,674	68,947	82,674	68,947
Loans held-for-investment	$ 0	$ 0	$ 0	0
Consumer and Other | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses at beginning of period				$ (1)
Allowance for credit losses at period end					$ (1)