Portfolio loans - Risk grades of portfolio loans by origination year (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Loans
Ending balance	$ 6,745,499	$ 6,687,249
Pass
Loans
Ending balance	6,078,957	5,997,126
Watch
Loans
Ending balance	370,337	413,876
Special Mention
Loans
Ending balance	192,470	181,107
Substandard
Loans
Ending balance	78,063	75,215
Substandard Non-accrual
Loans
Ending balance	25,672	27,896
Commercial
Loans
2020	210,141
2019	262,204
2018	183,942
2017	160,865
2016	98,726
Prior	159,910
Revolving loans	691,403
Ending balance	1,767,191
Commercial \| Pass
Loans
2020	183,585
2019	217,732
2018	158,089
2017	136,995
2016	84,025
Prior	129,623
Revolving loans	571,489
Ending balance	1,481,538	1,458,416
Commercial \| Watch
Loans
2020	11,686
2019	29,396
2018	17,424
2017	10,367
2016	4,617
Prior	12,958
Revolving loans	63,855
Ending balance	150,303	172,526
Commercial \| Special Mention
Loans
2020	12,010
2019	5,723
2018	1,918
2017	7,316
2016	7,148
Prior	15,166
Revolving loans	35,950
Ending balance	85,231	66,337
Commercial \| Substandard
Loans
2020	2,860
2019	6,108
2018	4,640
2017	5,646
2016	1,939
Prior	1,425
Revolving loans	20,109
Ending balance	42,727	41,273
Commercial \| Substandard Non-accrual
Loans
2019	3,245
2018	1,871
2017	541
2016	997
Prior	738
Ending balance	7,392	9,096
Commercial real estate
Loans
2020	193,049
2019	688,986
2018	549,549
2017	592,026
2016	290,597
Prior	473,327
Revolving loans	37,469
Ending balance	2,825,003
Commercial real estate \| Pass
Loans
2020	154,317
2019	597,120
2018	485,314
2017	551,251
2016	262,300
Prior	425,072
Revolving loans	33,927
Ending balance	2,509,301	2,477,398
Commercial real estate \| Watch
Loans
2020	20,142
2019	61,908
2018	37,717
2017	19,038
2016	19,039
Prior	17,375
Revolving loans	2,932
Ending balance	178,151	186,963
Commercial real estate \| Special Mention
Loans
2020	15,788
2019	15,758
2018	18,964
2017	14,042
2016	6,810
Prior	28,508
Revolving loans	495
Ending balance	100,365	105,487
Commercial real estate \| Substandard
Loans
2020	2,802
2019	12,855
2018	3,741
2017	6,211
2016	1,884
Prior	637
Revolving loans	115
Ending balance	28,245	26,204
Commercial real estate \| Substandard Non-accrual
Loans
2019	1,345
2018	3,813
2017	1,484
2016	564
Prior	1,735
Ending balance	8,941	9,178
Real estate construction
Loans
2020	39,792
2019	218,076
2018	142,631
2017	22,649
2016	778
Prior	1,541
Revolving loans	22,846
Ending balance	448,313
Real estate construction \| Pass
Loans
2020	26,489
2019	204,437
2018	139,119
2017	20,465
2016	412
Prior	1,534
Revolving loans	22,846
Ending balance	415,302	351,923
Real estate construction \| Watch
Loans
2020	10,936
2019	12,936
2018	2,582
2017	2,140
2016	214
Ending balance	28,808	45,262
Real estate construction \| Special Mention
Loans
2020	2,367
2019	703
2016	152
Ending balance	3,222	3,928
Real estate construction \| Substandard
Loans
2018	655
2017	44
Ending balance	699	737
Real estate construction \| Substandard Non-accrual
Loans
2018	275
Prior	7
Ending balance	282	630
Retail Real Estate
Loans
2020	51,945
2019	206,610
2018	202,618
2017	205,840
2016	188,679
Prior	391,629
Revolving loans	409,307
Ending balance	1,656,628
Retail Real Estate \| Pass
Loans
2020	51,441
2019	201,517
2018	199,235
2017	204,376
2016	184,629
Prior	381,085
Revolving loans	402,260
Ending balance	1,624,543	1,661,691
Retail Real Estate \| Watch
Loans
2020	296
2019	3,599
2018	1,893
2017	441
2016	1,034
Prior	736
Revolving loans	5,076
Ending balance	13,075	9,125
Retail Real Estate \| Special Mention
Loans
2020	108
2018	180
2016	2,001
Prior	1,363
Ending balance	3,652	5,355
Retail Real Estate \| Substandard
Loans
2019	1,285
2018	447
2017	537
2016	761
Prior	2,904
Revolving loans	453
Ending balance	6,387	7,001
Retail Real Estate \| Substandard Non-accrual
Loans
2020	100
2019	209
2018	863
2017	486
2016	254
Prior	5,541
Revolving loans	1,518
Ending balance	8,971	8,935
Retail Other
Loans
2020	6,142
2019	13,943
2018	9,331
2017	4,945
2016	1,618
Prior	1,419
Revolving loans	10,966
Ending balance	48,364
Retail Other \| Pass
Loans
2020	6,126
2019	13,896
2018	9,331
2017	4,942
2016	1,601
Prior	1,419
Revolving loans	10,958
Ending balance	48,273	47,698
Retail Other \| Substandard
Loans
Revolving loans	5
Ending balance	5
Retail Other \| Substandard Non-accrual
Loans
2020	16
2019	47
2017	3
2016	17
Revolving loans	3
Ending balance	86	57
Commercial Loans
Loans
Ending balance	1,767,191	1,748,368
Commercial Real Estate Loans
Loans
Ending balance	2,825,003	2,793,417
Real Estate Construction
Loans
Ending balance	448,313	401,861
Retail Real Estate
Loans
Ending balance	1,656,628	1,693,769
Retail Other
Loans
Ending balance	$ 48,364	$ 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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