Portfolio loans - Risk grades of portfolio loans by origination year (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Loans
Ending balance	$ 7,121,311	$ 6,687,249
Pass
Loans
Ending balance	6,421,496	5,997,126
Watch
Loans
Ending balance	439,044	413,876
Special Mention
Loans
Ending balance	158,929	181,107
Substandard
Loans
Ending balance	77,944	75,215
Substandard Non-accrual
Loans
Ending balance	23,898	27,896
Commercial
Loans
2020	1,068,734
2019	203,895
2018	139,632
2017	127,152
2016	79,541
Prior	117,060
Revolving loans	545,017
Ending balance	2,281,031
Commercial \| Pass
Loans
2020	1,029,324
2019	173,103
2018	117,434
2017	100,388
2016	67,473
Prior	87,096
Revolving loans	436,295
Ending balance	2,011,113	1,458,416
Commercial \| Watch
Loans
2020	24,601
2019	21,566
2018	16,918
2017	14,606
2016	3,488
Prior	13,653
Revolving loans	50,985
Ending balance	145,817	172,526
Commercial \| Special Mention
Loans
2020	6,011
2019	2,572
2018	2,166
2017	7,181
2016	6,853
Prior	14,949
Revolving loans	43,210
Ending balance	82,942	66,337
Commercial \| Substandard
Loans
2020	8,450
2019	3,578
2018	2,528
2017	4,437
2016	935
Prior	1,292
Revolving loans	12,027
Ending balance	33,247	41,273
Commercial \| Substandard Non-accrual
Loans
2020	348
2019	3,076
2018	586
2017	540
2016	792
Prior	70
Revolving loans	2,500
Ending balance	7,912	9,096
Commercial real estate
Loans
2020	638,670
2019	657,742
2018	496,672
2017	489,529
2016	245,647
Prior	359,689
Revolving loans	24,459
Ending balance	2,912,408
Commercial real estate \| Pass
Loans
2020	557,205
2019	565,460
2018	425,448
2017	439,438
2016	215,498
Prior	315,026
Revolving loans	23,380
Ending balance	2,541,455	2,477,398
Commercial real estate \| Watch
Loans
2020	52,304
2019	71,844
2018	62,609
2017	28,787
2016	21,629
Prior	18,186
Revolving loans	88
Ending balance	255,447	186,963
Commercial real estate \| Special Mention
Loans
2020	8,429
2019	14,981
2018	5,479
2017	12,664
2016	6,096
Prior	23,170
Revolving loans	496
Ending balance	71,315	105,487
Commercial real estate \| Substandard
Loans
2020	19,809
2019	4,662
2018	1,197
2017	7,165
2016	2,137
Prior	1,587
Revolving loans	495
Ending balance	37,052	26,204
Commercial real estate \| Substandard Non-accrual
Loans
2020	923
2019	795
2018	1,939
2017	1,475
2016	287
Prior	1,720
Ending balance	7,139	9,178
Real estate construction
Loans
2020	128,757
2019	192,531
2018	63,144
2017	3,418
2016	889
Prior	1,871
Revolving loans	16,656
Ending balance	407,266
Real estate construction \| Pass
Loans
2020	107,927
2019	188,254
2018	60,326
2017	1,188
2016	568
Prior	1,868
Revolving loans	16,656
Ending balance	376,787	351,923
Real estate construction \| Watch
Loans
2020	17,661
2019	4,266
2018	2,515
2017	2,205
2016	173
Ending balance	26,820	45,262
Real estate construction \| Special Mention
Loans
2020	592
2019	11
Ending balance	603	3,928
Real estate construction \| Substandard
Loans
2020	2,577
2018	47
2017	25
2016	148
Ending balance	2,797	737
Real estate construction \| Substandard Non-accrual
Loans
2018	256
Prior	3
Ending balance	259	630
Retail Real Estate
Loans
2020	277,755
2019	183,070
2018	155,124
2017	159,871
2016	161,165
Prior	301,328
Revolving loans	242,207
Ending balance	1,480,520
Retail Real Estate \| Pass
Loans
2020	273,752
2019	180,799
2018	152,772
2017	158,192
2016	157,611
Prior	293,570
Revolving loans	235,449
Ending balance	1,452,145	1,661,691
Retail Real Estate \| Watch
Loans
2020	1,570
2019	2,090
2018	1,255
2017	320
2016	570
Prior	255
Revolving loans	4,900
Ending balance	10,960	9,125
Retail Real Estate \| Special Mention
Loans
2020	516
2018	70
2017	589
2016	1,975
Prior	919
Ending balance	4,069	5,355
Retail Real Estate \| Substandard
Loans
2020	1,642
2019	100
2018	330
2017	82
2016	770
Prior	1,655
Revolving loans	269
Ending balance	4,848	7,001
Retail Real Estate \| Substandard Non-accrual
Loans
2020	275
2019	81
2018	697
2017	688
2016	239
Prior	4,929
Revolving loans	1,589
Ending balance	8,498	8,935
Retail Other
Loans
2020	6,989
2019	10,702
2018	6,798
2017	3,338
2016	962
Prior	841
Revolving loans	10,456
Ending balance	40,086
Retail Other \| Pass
Loans
2020	6,974
2019	10,695
2018	6,798
2017	3,336
2016	961
Prior	777
Revolving loans	10,455
Ending balance	39,996	47,698
Retail Other \| Substandard Non-accrual
Loans
2020	15
2019	7
2017	2
2016	1
Prior	64
Revolving loans	1
Ending balance	90	57
Commercial Loans
Loans
Ending balance	2,281,031	1,748,368
Commercial Real Estate Loans
Loans
Ending balance	2,912,408	2,793,417
Real Estate Construction
Loans
Ending balance	407,266	401,861
Retail Real Estate
Loans
Ending balance	1,480,520	1,693,769
Retail Other
Loans
Ending balance	$ 40,086	$ 49,834

Amount, before allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business.

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