Allowance for Credit Losses - Schedule of Activity in the Allowance for Credit Losses by Loan Portfolio (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses at beginning of period		$ 357,448	$ 299,653
Other adjustments		47	(108)
Charge-offs	$ (17,468)	(53,812)	(31,779)
Recoveries		8,310	11,503
Provision for credit losses		114,531	78,179
Allowance for credit losses at period end	427,265	427,265	$ 357,448
Accounting Standards Update [Extensible Enumeration]			Accounting Standards Update 2022-02
Individually evaluated for impairment	20,885	20,885	$ 6,799
Collectively evaluated for impairment	406,380	406,380	350,649
Individually evaluated for impairment	91,153	91,153	90,197
Collectively evaluated for impairment	41,885,417	41,885,417	38,926,356
Loans held-for-investment	155,261	155,261	$ 179,932
Accounting Standards Update 2022-02
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Accounting Standards Update [Extensible Enumeration]			Accounting Standards Update 2022-02
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		142,769	119,307
Other adjustments		0	0
Charge-offs		(15,713)	(14,141)
Recoveries		2,651	4,748
Provision for credit losses		39,786	32,855
Allowance for credit losses at period end	169,604	169,604	142,769
Individually evaluated for impairment	17,589	17,589	5,973
Collectively evaluated for impairment	152,015	152,015	136,796
Individually evaluated for impairment	38,940	38,940	38,042
Collectively evaluated for impairment	12,793,113	12,793,113	12,511,122
Loans held-for-investment	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		184,352	144,583
Other adjustments		0	0
Charge-offs		(15,228)	(1,379)
Recoveries		460	701
Provision for credit losses		52,913	40,447
Allowance for credit losses at period end	223,853	223,853	184,352
Individually evaluated for impairment	3,150	3,150	61
Collectively evaluated for impairment	220,703	220,703	184,291
Individually evaluated for impairment	35,459	35,459	21,435
Collectively evaluated for impairment	11,308,705	11,308,705	9,929,512
Loans held-for-investment	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		7,573	10,699
Other adjustments		0	0
Charge-offs		(227)	(432)
Recoveries		139	319
Provision for credit losses		(336)	(3,013)
Allowance for credit losses at period end	7,116	7,116	7,573
Individually evaluated for impairment	0	0	50
Collectively evaluated for impairment	7,116	7,116	7,523
Individually evaluated for impairment	1,341	1,341	10,351
Collectively evaluated for impairment	342,635	342,635	322,347
Loans held-for-investment	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		11,585	8,782
Other adjustments		0	0
Charge-offs		(192)	(471)
Recoveries		21	77
Provision for credit losses		2,411	3,197
Allowance for credit losses at period end	13,133	13,133	11,585
Individually evaluated for impairment	135	135	715
Collectively evaluated for impairment	12,998	12,998	10,870
Individually evaluated for impairment	15,391	15,391	20,300
Collectively evaluated for impairment	2,599,014	2,599,014	2,172,151
Loans held-for-investment	155,261	155,261	179,932
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 Receivable
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses at beginning of period		10,671	15,859
Other adjustments		47	(108)
Charge-offs		(21,857)	(14,275)
Recoveries		4,946	5,522
Provision for credit losses		19,262	3,673
Allowance for credit losses at period end	13,069	13,069	10,671
Individually evaluated for impairment	0	0	0
Collectively evaluated for impairment	13,069	13,069	10,671
Individually evaluated for impairment	0	0	0
Collectively evaluated for impairment	14,781,472	14,781,472	13,940,457
Loans held-for-investment	0	0	0
Premium Finance Receivable | 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		498	423
Other adjustments		0	0
Charge-offs		(595)	(1,081)
Recoveries		93	136
Provision for credit losses		495	1,020
Allowance for credit losses at period end	490	490	498
Individually evaluated for impairment	11	11	0
Collectively evaluated for impairment	479	479	498
Individually evaluated for impairment	22	22	69
Collectively evaluated for impairment	60,478	60,478	50,767
Loans held-for-investment	$ 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)