Allowance for Credit Losses (Summary of Activity in the Allowance for Credit Losses by Loan Portfolio) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses at beginning of period	$ 375,798	$ 301,168	$ 357,448	$ 299,653	$ 299,653
Other adjustments	41	(56)	45	(34)
Charge-offs	(18,516)	(12,316)	(25,867)	(17,041)
Recoveries	1,486	2,820	3,372	5,013
Provision for credit losses	28,571	20,493	51,641	24,518
Allowance for credit losses at period end	387,380	312,109	$ 387,380	312,109	$ 357,448
Cumulative effect adjustment from the adoption of ASU 2016-13, net of tax			Accounting Standards Update 2016-13 [Member]		Accounting Standards Update 2022-02
Individually measured	13,130	6,668	$ 13,130	6,668
Collectively measured	374,250	305,441	374,250	305,441
Loans at period end, individually evaluated for impairment	73,804	85,557	73,804	85,557
Loans at period end, collectively evaluated for impairment	40,749,157	36,844,789	40,749,157	36,844,789
Loans held-for-investment	200,447	122,757	200,447	122,757
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	149,501	120,911	142,769	119,307	119,307
Other adjustments	0	0	0	0
Charge-offs	(5,629)	(8,928)	(8,172)	(10,342)
Recoveries	505	996	897	1,534
Provision for credit losses	(1,235)	29,940	7,537	32,420
Allowance for credit losses at period end	143,142	142,919	143,142	142,919	142,769
Individually measured	7,205	5,674	7,205	5,674
Collectively measured	135,937	137,245	135,937	137,245
Loans at period end, individually evaluated for impairment	40,460	34,892	40,460	34,892
Loans at period end, collectively evaluated for impairment	12,560,011	12,012,213	12,560,011	12,012,213
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	194,780	144,906	184,352	144,583	144,583
Other adjustments	0	0	0	0
Charge-offs	(8,124)	(40)	(8,129)	(817)
Recoveries	25	553	125	585
Provision for credit losses	29,015	(1,687)	37,992	(619)
Allowance for credit losses at period end	215,696	143,732	215,696	143,732	184,352
Individually measured	5,819	99	5,819	99
Collectively measured	209,877	143,633	209,877	143,633
Loans at period end, individually evaluated for impairment	18,483	20,377	18,483	20,377
Loans at period end, collectively evaluated for impairment	10,590,328	9,386,828	10,590,328	9,386,828
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	7,728	10,566	7,573	10,699	10,699
Other adjustments	0	0	0	0
Charge-offs	0	(192)	0	(389)
Recoveries	37	123	72	216
Provision for credit losses	(798)	(3,507)	(645)	(3,536)
Allowance for credit losses at period end	6,967	6,990	6,967	6,990	7,573
Individually measured	0	105	0	105
Collectively measured	6,967	6,885	6,967	6,885
Loans at period end, individually evaluated for impairment	1,361	11,876	1,361	11,876
Loans at period end, collectively evaluated for impairment	335,613	313,950	335,613	313,950
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	11,434	9,429	11,585	8,782	8,782
Other adjustments	0	0	0	0
Charge-offs	0	0	0	(466)
Recoveries	6	6	10	11
Provision for credit losses	812	1,044	1,349	2,152
Allowance for credit losses at period end	12,252	10,479	12,252	10,479	11,585
Individually measured	106	790	106	790
Collectively measured	12,146	9,689	12,146	9,689
Loans at period end, individually evaluated for impairment	13,496	18,333	13,496	18,333
Loans at period end, collectively evaluated for impairment	2,429,297	1,937,817	2,429,297	1,937,817
Loans held-for-investment	200,447	122,757	200,447	122,757
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	11,955	14,722	10,671	15,859	15,859
Other adjustments	41	(56)	45	(34)
Charge-offs	(4,653)	(2,903)	(9,303)	(4,581)
Recoveries	890	1,119	2,213	2,595
Provision for credit losses	813	(5,380)	5,420	(6,337)
Allowance for credit losses at period end	9,046	7,502	9,046	7,502	10,671
Individually measured	0	0	0	0
Collectively measured	9,046	7,502	9,046	7,502
Loans at period end, individually evaluated for impairment	0	0	0	0
Loans at period end, collectively evaluated for impairment	14,801,971	13,149,880	14,801,971	13,149,880
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	400	634	498	423	423
Other adjustments	0	0	0	0
Charge-offs	(110)	(253)	(263)	(446)
Recoveries	23	23	55	72
Provision for credit losses	(36)	83	(12)	438
Allowance for credit losses at period end	277	487	277	487	498
Individually measured	0	0	0	0
Collectively measured	277	487	277	487
Loans at period end, individually evaluated for impairment	4	79	4	79
Loans at period end, collectively evaluated for impairment	31,937	44,101	31,937	44,101
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)