Portfolio loans - Risk grades of portfolio loans by origination year (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Loans
Ending balance	$ 7,229,020	$ 6,687,249
Pass
Loans
Ending balance	6,521,097	5,997,126
Watch
Loans
Ending balance	406,674	413,876
Special Mention
Loans
Ending balance	192,417	181,107
Substandard
Loans
Ending balance	83,737	75,215
Substandard Non-accrual
Loans
Ending balance	25,095	27,896
Commercial
Loans
2020	972,237
2019	228,310
2018	167,794
2017	151,219
2016	91,521
Prior	127,981
Revolving loans	618,892
Ending balance	2,357,954
Commercial \| Pass
Loans
2020	931,544
2019	193,072
2018	139,275
2017	129,906
2016	79,484
Prior	94,852
Revolving loans	510,151
Ending balance	2,078,284	1,458,416
Commercial \| Watch
Loans
2020	23,426
2019	22,915
2018	20,322
2017	8,145
2016	3,017
Prior	15,488
Revolving loans	43,504
Ending balance	136,817	172,526
Commercial \| Special Mention
Loans
2020	5,947
2019	5,442
2018	3,226
2017	7,039
2016	6,930
Prior	15,579
Revolving loans	50,276
Ending balance	94,439	66,337
Commercial \| Substandard
Loans
2020	11,291
2019	3,222
2018	4,258
2017	5,588
2016	1,286
Prior	1,372
Revolving loans	14,961
Ending balance	41,978	41,273
Commercial \| Substandard Non-accrual
Loans
2020	29
2019	3,659
2018	713
2017	541
2016	804
Prior	690
Ending balance	6,436	9,096
Commercial real estate
Loans
2020	385,739
2019	669,802
2018	543,329
2017	546,061
2016	263,134
Prior	407,453
Revolving loans	31,496
Ending balance	2,847,014
Commercial real estate \| Pass
Loans
2020	315,356
2019	577,080
2018	473,528
2017	496,679
2016	226,747
Prior	357,509
Revolving loans	29,290
Ending balance	2,476,189	2,477,398
Commercial real estate \| Watch
Loans
2020	40,462
2019	69,029
2018	44,938
2017	28,018
2016	27,333
Prior	23,329
Revolving loans	717
Ending balance	233,826	186,963
Commercial real estate \| Special Mention
Loans
2020	12,212
2019	16,494
2018	17,895
2017	14,233
2016	6,800
Prior	24,553
Revolving loans	1,489
Ending balance	93,676	105,487
Commercial real estate \| Substandard
Loans
2020	17,409
2019	5,862
2018	3,216
2017	5,635
2016	1,863
Prior	329
Ending balance	34,314	26,204
Commercial real estate \| Substandard Non-accrual
Loans
2020	300
2019	1,337
2018	3,752
2017	1,496
2016	391
Prior	1,733
Ending balance	9,009	9,178
Real estate construction
Loans
2020	74,004
2019	210,358
2018	125,235
2017	3,697
2016	762
Prior	1,304
Revolving loans	17,671
Ending balance	433,031
Real estate construction \| Pass
Loans
2020	61,660
2019	200,254
2018	122,501
2017	1,535
2016	407
Prior	1,299
Revolving loans	17,671
Ending balance	405,327	351,923
Real estate construction \| Watch
Loans
2020	9,071
2019	10,092
2018	2,411
2017	2,128
2016	205
Ending balance	23,907	45,262
Real estate construction \| Special Mention
Loans
2020	673
2019	12
Ending balance	685	3,928
Real estate construction \| Substandard
Loans
2020	2,600
2018	48
2017	34
2016	150
Ending balance	2,832	737
Real estate construction \| Substandard Non-accrual
Loans
2018	275
Prior	5
Ending balance	280	630
Retail Real Estate
Loans
2020	235,525
2019	189,596
2018	176,098
2017	177,869
2016	171,858
Prior	348,711
Revolving loans	248,558
Ending balance	1,548,215
Retail Real Estate \| Pass
Loans
2020	232,130
2019	186,986
2018	172,855
2017	176,644
2016	167,885
Prior	340,407
Revolving loans	241,737
Ending balance	1,518,644	1,661,691
Retail Real Estate \| Watch
Loans
2020	1,102
2019	2,221
2018	1,943
2017	333
2016	986
Prior	722
Revolving loans	4,817
Ending balance	12,124	9,125
Retail Real Estate \| Special Mention
Loans
2020	526
2018	174
2016	1,988
Prior	929
Ending balance	3,617	5,355
Retail Real Estate \| Substandard
Loans
2020	1,487
2019	214
2018	333
2017	160
2016	751
Prior	1,216
Revolving loans	452
Ending balance	4,613	7,001
Retail Real Estate \| Substandard Non-accrual
Loans
2020	280
2019	175
2018	793
2017	732
2016	248
Prior	5,437
Revolving loans	1,552
Ending balance	9,217	8,935
Retail Other
Loans
2020	6,164
2019	12,367
2018	8,099
2017	4,081
2016	1,270
Prior	1,147
Revolving loans	9,678
Ending balance	42,806
Retail Other \| Pass
Loans
2020	6,101
2019	12,360
2018	8,099
2017	4,079
2016	1,253
Prior	1,084
Revolving loans	9,677
Ending balance	42,653	47,698
Retail Other \| Substandard Non-accrual
Loans
2020	63
2019	7
2017	2
2016	17
Prior	63
Revolving loans	1
Ending balance	153	57
Commercial Loans
Loans
Ending balance	2,357,954	1,748,368
Commercial Real Estate Loans
Loans
Ending balance	2,847,014	2,793,417
Real Estate Construction
Loans
Ending balance	433,031	401,861
Retail Real Estate
Loans
Ending balance	1,548,215	1,693,769
Retail Other
Loans
Ending balance	$ 42,806	$ 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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