Loans and Allowance for Credit Losses - Class of loan, an aging analysis and the recorded investments in loans past due (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current Loans	$ 7,796,448	$ 7,470,755
Loans Past Due	25,747	26,264
Non-Accrual	58,060	48,729
Financing Receivable, after Allowance for Credit Loss	7,880,255	7,545,748
C & I Owner Occupied
Current Loans	138,837
Loans Past Due	1,520
Non-Accrual	0
Financing Receivable, after Allowance for Credit Loss	140,357
Commercial
Current Loans	1,494,038	1,527,134
Loans Past Due	14,739	3,844
Non-Accrual	15,836	14,928
Financing Receivable, after Allowance for Credit Loss	1,524,613	1,545,906
PPP loans
Current Loans	456,115
Non-Accrual	0	0
Financing Receivable, after Allowance for Credit Loss	456,115
Income producing - commercial real estate
Current Loans	3,696,949	3,687,494
Loans Past Due	7,822	5,542
Non-Accrual	20,068	9,711
Financing Receivable, after Allowance for Credit Loss	3,724,839	3,702,747
Owner occupied - Commercial real estate
Current Loans	983,021	965,938
Loans Past Due	446	13,008
Non-Accrual	14,178	6,463
Financing Receivable, after Allowance for Credit Loss	997,645	985,409
Real estate mortgage residential
Current Loans	76,798	95,057
Loans Past Due		3,533
Non-Accrual	5,587	5,631
Financing Receivable, after Allowance for Credit Loss	82,385	104,221
Construction - commercial and residential
Current Loans	876,361	1,113,735
Loans Past Due	509
Non-Accrual	2,274	11,509
Financing Receivable, after Allowance for Credit Loss	879,144	1,125,244
Home equity
Current Loans	71,837	79,246
Loans Past Due	702	328
Non-Accrual	109	487
Financing Receivable, after Allowance for Credit Loss	72,648	80,061
Other consumer
Current Loans	2,492	2,151
Loans Past Due	9	9
Non-Accrual	8	0
Financing Receivable, after Allowance for Credit Loss	2,509	2,160
30 to 59 days past due
Loans Past Due	6,770	19,740
30 to 59 days past due | C & I Owner Occupied
Loans Past Due	1,520
30 to 59 days past due | Commercial
Loans Past Due	4,585	3,063
30 to 59 days past due | Owner occupied - Commercial real estate
Loans Past Due	0	13,008
30 to 59 days past due | Real estate mortgage residential
Loans Past Due		3,533
30 to 59 days past due | Home equity
Loans Past Due	656	136
60-89 days past due
Loans Past Due	18,977	6,524
60-89 days past due | Commercial
Loans Past Due	10,154	781
60-89 days past due | Income producing - commercial real estate
Loans Past Due	7,822	5,542
60-89 days past due | Owner occupied - Commercial real estate
Loans Past Due	446
60-89 days past due | Construction - commercial and residential
Loans Past Due	509
60-89 days past due | Home equity
Loans Past Due	46	192
60-89 days past due | Other consumer
Loans Past Due	$ 0	$ 9