Loans and Leases and Allowance for Credit Losses - Aging of amortized cost basis in loans by aging category and accrual status (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Loans by aging category
Total loans	$ 11,798,910	$ 8,812,553
Commercial | Owner occupied commercial real estate
Loans by aging category
Total loans	2,008,674
Commercial | Income producing commercial real estate
Loans by aging category
Total loans	2,493,625
Commercial | Commercial & industrial
Loans by aging category
Total loans	3,104,868
Commercial | Construction
Loans by aging category
Total loans	981,371
Commercial | Equipment financing
Loans by aging category
Total loans	823,022
Residential | Construction
Loans by aging category
Total loans	263,266
Residential | Residential mortgage
Loans by aging category
Total loans	1,269,548
Residential | Home equity lines of credit
Loans by aging category
Total loans	706,877
Consumer
Loans by aging category
Total loans	147,659
Loans receivable
Loans by aging category
Current Loans	11,737,229	8,712,667
Nonaccrual Loans	49,084	35,341
Total loans	11,798,910	8,812,553
Loans receivable | Loans Past Due, 30 - 59 Days
Loans by aging category
Loans Past Due	10,145
Loans receivable | Loans Past Due, 60 - 89 Days
Loans by aging category
Loans Past Due	2,452
Loans receivable | Loans Past Due, over 90 Days
Loans by aging category
Loans Past Due	0
Loans receivable | Commercial
Loans by aging category
Current Loans	9,372,656	6,596,675
Nonaccrual Loans	31,839	20,503
Total loans	9,411,560	6,669,593
Loans receivable | Commercial | Loans Past Due, 30 - 59 Days
Loans by aging category
Loans Past Due	5,218
Loans receivable | Commercial | Loans Past Due, 60 - 89 Days
Loans by aging category
Loans Past Due	1,847
Loans receivable | Commercial | Loans Past Due, over 90 Days
Loans by aging category
Loans Past Due	0
Loans receivable | Commercial | Owner occupied commercial real estate
Loans by aging category
Current Loans	1,996,903	1,700,682
Nonaccrual Loans	11,075	10,544
Total loans	2,008,674	1,720,227
Loans receivable | Commercial | Owner occupied commercial real estate | Loans Past Due, 30 - 59 Days
Loans by aging category
Loans Past Due	585
Loans receivable | Commercial | Owner occupied commercial real estate | Loans Past Due, 60 - 89 Days
Loans by aging category
Loans Past Due	111
Loans receivable | Commercial | Owner occupied commercial real estate | Loans Past Due, over 90 Days
Loans by aging category
Loans Past Due	0
Loans receivable | Commercial | Income producing commercial real estate
Loans by aging category
Current Loans	2,479,614	1,979,053
Nonaccrual Loans	12,230	1,996
Total loans	2,493,625	2,007,950
Loans receivable | Commercial | Income producing commercial real estate | Loans Past Due, 30 - 59 Days
Loans by aging category
Loans Past Due	996
Loans receivable | Commercial | Income producing commercial real estate | Loans Past Due, 60 - 89 Days
Loans by aging category
Loans Past Due	785
Loans receivable | Commercial | Income producing commercial real estate | Loans Past Due, over 90 Days
Loans by aging category
Loans Past Due	0
Loans receivable | Commercial | Commercial & industrial
Loans by aging category
Current Loans	3,099,387	1,215,581
Nonaccrual Loans	3,534	2,545
Total loans	3,104,868	1,220,657
Loans receivable | Commercial | Commercial & industrial | Loans Past Due, 30 - 59 Days
Loans by aging category
Loans Past Due	1,882
Loans receivable | Commercial | Commercial & industrial | Loans Past Due, 60 - 89 Days
Loans by aging category
Loans Past Due	65
Loans receivable | Commercial | Commercial & industrial | Loans Past Due, over 90 Days
Loans by aging category
Loans Past Due	0
Loans receivable | Commercial | Construction
Loans by aging category
Current Loans	979,169	966,833
Nonaccrual Loans	1,863	2,277
Total loans	981,371	976,215
Loans receivable | Commercial | Construction | Loans Past Due, 30 - 59 Days
Loans by aging category
Loans Past Due	339
Loans receivable | Commercial | Construction | Loans Past Due, 60 - 89 Days
Loans by aging category
Loans Past Due	0
Loans receivable | Commercial | Construction | Loans Past Due, over 90 Days
Loans by aging category
Loans Past Due	0
Loans receivable | Commercial | Equipment financing
Loans by aging category
Current Loans	817,583	734,526
Nonaccrual Loans	3,137	3,141
Total loans	823,022	744,544
Loans receivable | Commercial | Equipment financing | Loans Past Due, 30 - 59 Days
Loans by aging category
Loans Past Due	1,416
Loans receivable | Commercial | Equipment financing | Loans Past Due, 60 - 89 Days
Loans by aging category
Loans Past Due	886
Loans receivable | Commercial | Equipment financing | Loans Past Due, over 90 Days
Loans by aging category
Loans Past Due	0
Loans receivable | Residential | Construction
Loans by aging category
Current Loans	262,002	235,211
Nonaccrual Loans	479	939
Total loans	263,266	236,437
Loans receivable | Residential | Construction | Loans Past Due, 30 - 59 Days
Loans by aging category
Loans Past Due	712
Loans receivable | Residential | Construction | Loans Past Due, 60 - 89 Days
Loans by aging category
Loans Past Due	73
Loans receivable | Residential | Construction | Loans Past Due, over 90 Days
Loans by aging category
Loans Past Due	0
Loans receivable | Residential | Residential mortgage
Loans by aging category
Current Loans	1,252,937	1,097,999
Nonaccrual Loans	13,864	10,567
Total loans	1,269,548	1,117,616
Loans receivable | Residential | Residential mortgage | Loans Past Due, 30 - 59 Days
Loans by aging category
Loans Past Due	2,481
Loans receivable | Residential | Residential mortgage | Loans Past Due, 60 - 89 Days
Loans by aging category
Loans Past Due	266
Loans receivable | Residential | Residential mortgage | Loans Past Due, over 90 Days
Loans by aging category
Loans Past Due	0
Loans receivable | Residential | Home equity lines of credit
Loans by aging category
Current Loans	702,457	655,762
Nonaccrual Loans	2,642	3,173
Total loans	706,877	660,675
Loans receivable | Residential | Home equity lines of credit | Loans Past Due, 30 - 59 Days
Loans by aging category
Loans Past Due	1,532
Loans receivable | Residential | Home equity lines of credit | Loans Past Due, 60 - 89 Days
Loans by aging category
Loans Past Due	246
Loans receivable | Residential | Home equity lines of credit | Loans Past Due, over 90 Days
Loans by aging category
Loans Past Due	0
Loans receivable | Consumer
Loans by aging category
Current Loans	147,177	127,020
Nonaccrual Loans	260	159
Total loans	147,659	$ 128,232
Loans receivable | Consumer | Loans Past Due, 30 - 59 Days
Loans by aging category
Loans Past Due	202
Loans receivable | Consumer | Loans Past Due, 60 - 89 Days
Loans by aging category
Loans Past Due	20
Loans receivable | Consumer | Loans Past Due, over 90 Days
Loans by aging category
Loans Past Due	$ 0