Loans and Allowance for Credit Losses - Risk category of loans by class of loans (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Prior	$ 1,857,809
2016	750,571
2017	1,299,313
2018	1,621,689
2019	1,227,746
2020	1,123,127
Loans	7,880,255	$ 7,545,748
Pass
Loans		7,356,769
Watch
Loans		109,313
Special Mention
Loans		11,460
Substandard
Loans		68,206
Commercial
Prior	426,495
2016	132,569
2017	340,932
2018	271,637
2019	197,475
2020	155,505
Loans	1,524,613	1,545,906
Commercial | Pass
Prior	375,848
2016	124,678
2017	306,487
2018	249,287
2019	193,594
2020	155,505
Loans	1,405,399	1,470,636
Commercial | Watch
Prior	32,430
2018	451
Loans	32,881	38,522
Commercial | Special Mention
Prior	1,302
2016	4,766
2017	2,046
2018	12,421
2019	207
Loans	20,742	11,460
Commercial | Substandard
Prior	16,915
2016	3,125
2017	32,399
2018	9,478
2019	3,674
Loans	65,591	25,288
PPP loans
2020	456,115
Loans	456,115	0
PPP loans | Pass
2020	456,115
Loans	456,115
Income producing - commercial real estate
Prior	919,795
2016	418,970
2017	500,252
2018	744,303
2019	763,798
2020	377,721
Loans	3,724,839	3,702,747
Income producing - commercial real estate | Pass
Prior	756,002
2016	402,690
2017	421,428
2018	685,804
2019	705,972
2020	377,721
Loans	3,349,617	3,667,585
Income producing - commercial real estate | Watch
Prior	150,215
2019	47,644
Loans	197,859	16,069
Income producing - commercial real estate | Special Mention
Prior	203
2016	800
2017	4,656
2018	4,883
2019	5,542
Loans	16,084
Income producing - commercial real estate | Substandard
Prior	13,375
2016	15,480
2017	74,168
2018	53,616
2019	4,640
Loans	161,279	19,093
Owner occupied - Commercial real estate
Prior	404,465
2016	108,183
2017	117,789
2018	235,517
2019	102,522
2020	29,169
Loans	997,645	985,409
Owner occupied - Commercial real estate | Pass
Prior	344,863
2016	105,381
2017	115,144
2018	139,991
2019	74,286
2020	29,169
Loans	808,834	925,800
Owner occupied - Commercial real estate | Watch
Prior	50,018
2016	764
2018	355
2019	3,475
Loans	54,612	53,146
Owner occupied - Commercial real estate | Substandard
Prior	9,584
2016	2,038
2017	2,645
2018	95,171
2019	24,761
Loans	134,199	6,463
Real estate mortgage residential
Prior	19,914
2016	7,564
2017	10,377
2018	14,593
2019	23,100
2020	6,837
Loans	82,385	104,221
Real estate mortgage residential | Pass
Prior	18,121
2016	3,410
2017	10,377
2018	14,593
2019	23,100
2020	6,837
Loans	76,438	98,228
Real estate mortgage residential | Watch
Prior	612
2016	4,154
Loans	4,766	628
Real estate mortgage residential | Substandard
Prior	1,181
Loans	1,181	5,365
Construction - commercial and residential
Prior	33,388
2016	67,569
2017	312,959
2018	314,061
2019	104,335
2020	46,832
Loans	879,144	1,125,244
Construction - commercial and residential | Pass
Prior	32,535
2016	65,703
2017	286,922
2018	314,061
2019	104,335
2020	46,832
Loans	850,388	1,113,734
Construction - commercial and residential | Watch
Prior	0
2017	25,629
Loans	25,629
Construction - commercial and residential | Substandard
2016	1,866
2017	408
Loans	3,127	11,510
C & I Owner Occupied
Prior	11,949
2016	10,577
2017	8,622
2018	33,214
2019	31,998
2020	43,997
Loans	140,357
C & I Owner Occupied | Pass
Prior	11,162
2016	10,577
2017	6,501
2018	29,963
2019	18,761
2020	43,997
Loans	120,961
C & I Owner Occupied | Watch
Prior	787
2017	2,121
2018	3,251
2019	13,237
Loans	19,396
Home equity
Prior	39,754
2016	4,970
2017	8,274
2018	8,314
2019	4,418
2020	6,918
Loans	72,648	80,061
Home equity | Pass
Prior	38,049
2016	4,970
2017	8,274
2018	8,314
2019	4,369
2020	6,918
Loans	70,894	78,626
Home equity | Watch
Prior	1,401
Loans	1,450	948
Home equity | Substandard
Prior	304
Loans	304	487
Other consumer
Prior	2,049
2016	169
2017	108
2018	50
2019	100
2020	33
Loans	2,509	2,160
Other consumer | Pass
Prior	2,039
2016	169
2017	108
2018	50
2019	100
2020	33
Loans	2,499	$ 2,160
Other consumer | Substandard
Prior	10
Loans	$ 10