Past Due Loans, Allowance For Credit Losses, Non-Accrual Loans, and TDRS - Corporate Loans Portfolio Segment By Origination Year (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Dec. 31, 2019
Total loans
Total Loans	$ 14,653,188	$ 14,653,188	$ 12,840,330
Consumer net loan charge-offs
Revolving loans converted to term loans	5,200	29,000
Corporate Loan | Commercial industrial and agricultural
Total loans
2020	561,820	561,820
2019	877,227	877,227
2018	938,801	938,801
2017	528,347	528,347
2016	252,263	252,263
Prior	471,873	471,873
Revolving Loans	1,382,706	1,382,706
Total Loans	5,013,037	5,013,037
Corporate Loan | Commercial industrial and agricultural | Pass
Total loans
2020	554,985	554,985
2019	850,903	850,903
2018	810,527	810,527
2017	487,372	487,372
2016	212,757	212,757
Prior	424,072	424,072
Revolving Loans	1,214,399	1,214,399
Total Loans	4,555,015	4,555,015
Corporate Loan | Commercial industrial and agricultural | Special Mention
Total loans
2020	6,498	6,498
2019	18,569	18,569
2018	41,688	41,688
2017	9,943	9,943
2016	21,798	21,798
Prior	17,137	17,137
Revolving Loans	115,293	115,293
Total Loans	230,926	230,926
Corporate Loan | Commercial industrial and agricultural | Substandard
Total loans
2020	337	337
2019	3,855	3,855
2018	62,921	62,921
2017	21,842	21,842
2016	16,511	16,511
Prior	23,337	23,337
Revolving Loans	35,134	35,134
Total Loans	163,937	163,937
Corporate Loan | Commercial industrial and agricultural | Non-accrual
Total loans
2020	0	0
2019	3,900	3,900
2018	23,665	23,665
2017	9,190	9,190
2016	1,197	1,197
Prior	7,327	7,327
Revolving Loans	17,880	17,880
Total Loans	63,159	63,159
Corporate Loan | Commercial industrial and agricultural | Net loan charge-offs
Total loans
2020	0	0
2019	586	586
2018	1,431	1,431
2017	1,626	1,626
2016	1,934	1,934
Prior	1,589	1,589
Revolving Loans	9,329	9,329
Total Loans	16,495	16,495
Corporate Loan | Office, retail, and industrial
Total loans
2020	116,868	116,868
2019	263,954	263,954
2018	222,727	222,727
2017	324,613	324,613
2016	323,664	323,664
Prior	692,716	692,716
Revolving Loans	5,864	5,864
Total Loans	1,950,406	1,950,406
Corporate Loan | Office, retail, and industrial | Pass
Total loans
2020	115,443	115,443
2019	263,308	263,308
2018	218,204	218,204
2017	312,063	312,063
2016	287,643	287,643
Prior	628,127	628,127
Revolving Loans	5,664	5,664
Total Loans	1,830,452	1,830,452
Corporate Loan | Office, retail, and industrial | Special Mention
Total loans
2020	1,425	1,425
2019	646	646
2018	4,392	4,392
2017	12,086	12,086
2016	24,284	24,284
Prior	17,765	17,765
Revolving Loans	200	200
Total Loans	60,798	60,798
Corporate Loan | Office, retail, and industrial | Substandard
Total loans
2020	0	0
2019	0	0
2018	0	0
2017	283	283
2016	1,499	1,499
Prior	22,133	22,133
Revolving Loans	0	0
Total Loans	23,915	23,915
Corporate Loan | Office, retail, and industrial | Non-accrual
Total loans
2020	0	0
2019	0	0
2018	131	131
2017	181	181
2016	10,238	10,238
Prior	24,691	24,691
Revolving Loans	0	0
Total Loans	35,241	35,241
Corporate Loan | Office, retail, and industrial | Net loan charge-offs
Total loans
2020	0	0
2019	333	333
2018	155	155
2017	5	5
2016	1,628	1,628
Prior	2,633	2,633
Revolving Loans	0	0
Total Loans	4,754	4,754
Corporate Loan | Multi-family
Total loans
2020	134,824	134,824
2019	171,670	171,670
2018	82,845	82,845
2017	112,861	112,861
2016	92,920	92,920
Prior	245,662	245,662
Revolving Loans	27,511	27,511
Total Loans	868,293	868,293
Corporate Loan | Multi-family | Pass
Total loans
2020	134,824	134,824
2019	171,572	171,572
2018	82,460	82,460
2017	111,504	111,504
2016	87,424	87,424
Prior	236,960	236,960
Revolving Loans	27,511	27,511
Total Loans	852,255	852,255
Corporate Loan | Multi-family | Special Mention
Total loans
2020	0	0
2019	98	98
2018	0	0
2017	0	0
2016	5,496	5,496
Prior	2,170	2,170
Revolving Loans	0	0
Total Loans	7,764	7,764
Corporate Loan | Multi-family | Substandard
Total loans
2020	0	0
2019	0	0
2018	385	385
2017	78	78
2016	0	0
Prior	5,378	5,378
Revolving Loans	0	0
Total Loans	5,841	5,841
Corporate Loan | Multi-family | Non-accrual
Total loans
2020	0	0
2019	0	0
2018	0	0
2017	1,279	1,279
2016	0	0
Prior	1,154	1,154
Revolving Loans	0	0
Total Loans	2,433	2,433
Corporate Loan | Multi-family | Net loan charge-offs
Total loans
2020	0	0
2019	3	3
2018	0	0
2017	1	1
2016	0	0
Prior	10	10
Revolving Loans	0	0
Total Loans	14	14
Corporate Loan | Construction
Total loans
2020	56,790	56,790
2019	129,311	129,311
2018	172,899	172,899
2017	93,900	93,900
2016	71,574	71,574
Prior	75,980	75,980
Revolving Loans	31,153	31,153
Total Loans	631,607	631,607
Corporate Loan | Construction | Pass
Total loans
2020	56,790	56,790
2019	129,311	129,311
2018	172,855	172,855
2017	82,528	82,528
2016	57,401	57,401
Prior	65,769	65,769
Revolving Loans	29,494	29,494
Total Loans	594,148	594,148
Corporate Loan | Construction | Special Mention
Total loans
2020	0	0
2019	0	0
2018	44	44
2017	3,655	3,655
2016	3,838	3,838
Prior	1,286	1,286
Revolving Loans	0	0
Total Loans	8,823	8,823
Corporate Loan | Construction | Substandard
Total loans
2020	0	0
2019	0	0
2018	0	0
2017	7,717	7,717
2016	10,335	10,335
Prior	4,138	4,138
Revolving Loans	0	0
Total Loans	22,190	22,190
Corporate Loan | Construction | Non-accrual
Total loans
2020	0	0
2019	0	0
2018	0	0
2017	0	0
2016	0	0
Prior	4,787	4,787
Revolving Loans	1,659	1,659
Total Loans	6,446	6,446
Corporate Loan | Construction | Net loan charge-offs
Total loans
2020	0	0
2019	118	118
2018	0	0
2017	5,490	5,490
2016	0	0
Prior	1,887	1,887
Revolving Loans	0	0
Total Loans	7,495	7,495
Corporate Loan | Other commercial real estate
Total loans
2020	114,175	114,175
2019	189,202	189,202
2018	270,609	270,609
2017	219,049	219,049
2016	137,375	137,375
Prior	495,768	495,768
Revolving Loans	26,816	26,816
Total Loans	1,452,994	1,452,994
Corporate Loan | Other commercial real estate | Pass
Total loans
2020	114,175	114,175
2019	183,856	183,856
2018	227,370	227,370
2017	201,760	201,760
2016	117,615	117,615
Prior	381,532	381,532
Revolving Loans	26,480	26,480
Total Loans	1,252,788	1,252,788
Corporate Loan | Other commercial real estate | Special Mention
Total loans
2020	0	0
2019	3,863	3,863
2018	19,906	19,906
2017	7,574	7,574
2016	7,874	7,874
Prior	47,524	47,524
Revolving Loans	243	243
Total Loans	86,984	86,984
Corporate Loan | Other commercial real estate | Substandard
Total loans
2020	0	0
2019	1,483	1,483
2018	22,662	22,662
2017	6,400	6,400
2016	10,341	10,341
Prior	54,661	54,661
Revolving Loans	0	0
Total Loans	95,547	95,547
Corporate Loan | Other commercial real estate | Non-accrual
Total loans
2020	0	0
2019	0	0
2018	671	671
2017	3,315	3,315
2016	1,545	1,545
Prior	12,051	12,051
Revolving Loans	93	93
Total Loans	17,675	17,675
Corporate Loan | Other commercial real estate | Net loan charge-offs
Total loans
2020	0	0
2019	430	430
2018	179	179
2017	366	366
2016	183	183
Prior	778	778
Revolving Loans	0	0
Total Loans	1,936	1,936
Consumer loans
Total loans
Total Loans	3,540,313	3,540,313	3,271,117
Consumer loans | Home equity
Total loans
2020	11,158	11,158
2019	12,769	12,769
2018	15,429	15,429
2017	12,922	12,922
2016	10,707	10,707
Prior	65,398	65,398
Revolving Loans	699,363	699,363
Total Loans	827,746	827,746	851,454
Consumer net loan charge-offs
2020	0	0
2019	0	0
2018	1	1
2017	(1)	(1)
2016	1	1
Prior	(61)	(61)
Financing Receivable, Revolving, Net Loan Charge-Offs	(21)	(21)
Total	(81)	(81)
Consumer loans | Home equity | Performing
Total loans
2020	11,158	11,158
2019	12,747	12,747
2018	15,191	15,191
2017	12,661	12,661
2016	10,187	10,187
Prior	58,265	58,265
Revolving Loans	697,989	697,989
Total Loans	818,198	818,198
Consumer loans | Home equity | Non-accrual
Total loans
2020	0	0
2019	22	22
2018	238	238
2017	261	261
2016	520	520
Prior	7,133	7,133
Revolving Loans	1,374	1,374
Total Loans	9,548	9,548
Consumer loans | 1-4 family mortgages
Total loans
2020	794,744	794,744
2019	670,925	670,925
2018	261,689	261,689
2017	146,820	146,820
2016	176,843	176,843
Prior	236,534	236,534
Revolving Loans	0	0
Total Loans	2,287,555	2,287,555
Consumer net loan charge-offs
2020	0	0
2019	0	0
2018	32	32
2017	0	0
2016	7	7
Prior	729	729
Financing Receivable, Revolving, Net Loan Charge-Offs	0	0
Total	768	768
Consumer loans | 1-4 family mortgages | Performing
Total loans
2020	794,744	794,744
2019	670,925	670,925
2018	261,250	261,250
2017	146,737	146,737
2016	176,780	176,780
Prior	228,049	228,049
Revolving Loans	0	0
Total Loans	2,278,485	2,278,485
Consumer loans | 1-4 family mortgages | Non-accrual
Total loans
2020	0	0
2019	0	0
2018	439	439
2017	83	83
2016	63	63
Prior	8,485	8,485
Revolving Loans	0	0
Total Loans	9,070	9,070
Consumer loans | Installment
Total loans
2020	76,270	76,270
2019	169,380	169,380
2018	93,266	93,266
2017	38,384	38,384
2016	14,695	14,695
Prior	12,492	12,492
Revolving Loans	20,525	20,525
Total Loans	425,012	425,012	$ 492,585
Consumer net loan charge-offs
2020	190	190
2019	4,995	4,995
2018	2,835	2,835
2017	885	885
2016	85	85
Prior	373	373
Financing Receivable, Revolving, Net Loan Charge-Offs	36	36
Total	9,399	9,399
Consumer loans | Installment | Performing
Total loans
2020	76,270	76,270
2019	169,380	169,380
2018	93,266	93,266
2017	38,384	38,384
2016	14,695	14,695
Prior	12,492	12,492
Revolving Loans	20,525	20,525
Total Loans	425,012	425,012
Consumer loans | Installment | Non-accrual
Total loans
2020	0	0
2019	0	0
2018	0	0
2017	0	0
2016	0	0
Prior	0	0
Revolving Loans	0	0
Total Loans	$ 0	$ 0