Loans and Leases and Allowance for Credit Losses - Recorded investment in loans by portfolio segment and the balance of the allowance for loan losses (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans Outstanding, Individually evaluated for impairment			$ 61,971
Loans Outstanding, Collectively evaluated for impairment			8,691,936
PCI Loans			58,646
Total	$ 11,798,910		8,812,553
Allowance for credit losses, Individually evaluated for impairment			2,512
Allowance for credit losses, Collectively evaluated for impairment			59,214
Allowance for credit losses, PCI			363
Allowance for credit losses, Ending balance	134,256		62,089	$ 62,514		$ 61,203
Allowance for unfunded commitments, Individually evaluated for impairment			0
Allowance for unfunded commitments, Collectively evaluated for impairment			3,458
Allowance for unfunded commitments, Ending Balance	11,920	$ 12,100	3,458	3,458	$ 3,391	3,410
Total allowance for credit losses, Individually evaluated for impairment			2,512
Total allowance for credit losses, Collectively evaluated for impairment			62,672
Total allowance for credit losses, PCI			363
Total allowance for credit losses, Ending Balance	146,176	115,769	65,547	65,972	65,595	64,613
Commercial | Owner occupied commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	2,008,674
Commercial | Income producing commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	2,493,625
Commercial | Commercial & industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	3,104,868
Commercial | Construction
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	981,371
Commercial | Equipment financing
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	823,022
Residential | Construction
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	263,266
Residential | Residential mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	1,269,548
Residential | Home equity lines of credit
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	706,877
Consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	147,659
Loans receivable
Financing Receivable, Allowance for Credit Loss [Line Items]
PCI Loans			58,646
Total	11,798,910		8,812,553
Allowance for credit losses, Ending balance	134,256	103,669		62,514	62,204
Loans receivable | Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
PCI Loans			46,947
Total	9,411,560		6,669,593
Loans receivable | Commercial | Owner occupied commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans Outstanding, Individually evaluated for impairment			19,233
Loans Outstanding, Collectively evaluated for impairment			1,692,448
PCI Loans			8,546
Total	2,008,674		1,720,227
Allowance for credit losses, Individually evaluated for impairment			816
Allowance for credit losses, Collectively evaluated for impairment			10,483
Allowance for credit losses, PCI			105
Allowance for credit losses, Ending balance	19,374	14,592	11,404	11,419	11,545	12,207
Loans receivable | Commercial | Income producing commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans Outstanding, Individually evaluated for impairment			18,134
Loans Outstanding, Collectively evaluated for impairment			1,962,588
PCI Loans			27,228
Total	2,493,625		2,007,950
Allowance for credit losses, Individually evaluated for impairment			770
Allowance for credit losses, Collectively evaluated for impairment			11,507
Allowance for credit losses, PCI			29
Allowance for credit losses, Ending balance	35,038	21,699	12,306	11,062	11,020	11,073
Loans receivable | Commercial | Commercial & industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans Outstanding, Individually evaluated for impairment			1,449
Loans Outstanding, Collectively evaluated for impairment			1,218,882
PCI Loans			326
Total	3,104,868		1,220,657
Allowance for credit losses, Individually evaluated for impairment			21
Allowance for credit losses, Collectively evaluated for impairment			5,193
Allowance for credit losses, PCI			52
Allowance for credit losses, Ending balance	21,524	8,589	5,266	5,390	5,308	4,802
Loans receivable | Commercial | Construction
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans Outstanding, Individually evaluated for impairment			3,675
Loans Outstanding, Collectively evaluated for impairment			965,678
PCI Loans			6,862
Total	981,371		976,215
Allowance for credit losses, Individually evaluated for impairment			55
Allowance for credit losses, Collectively evaluated for impairment			9,613
Allowance for credit losses, PCI			0
Allowance for credit losses, Ending balance	14,851	14,514	9,668	10,407	10,318	10,337
Loans receivable | Commercial | Equipment financing
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans Outstanding, Individually evaluated for impairment			1,027
Loans Outstanding, Collectively evaluated for impairment			739,532
PCI Loans			3,985
Total	823,022		744,544
Allowance for credit losses, Individually evaluated for impairment			0
Allowance for credit losses, Collectively evaluated for impairment			7,240
Allowance for credit losses, PCI			144
Allowance for credit losses, Ending balance	15,176	20,305	7,384	7,246	6,935	5,452
Loans receivable | Residential | Construction
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans Outstanding, Individually evaluated for impairment			1,256
Loans Outstanding, Collectively evaluated for impairment			234,807
PCI Loans			374
Total	263,266		236,437
Allowance for credit losses, Individually evaluated for impairment			47
Allowance for credit losses, Collectively evaluated for impairment			2,456
Allowance for credit losses, PCI			1
Allowance for credit losses, Ending balance	1,768	1,997	2,504	2,551	2,365	2,433
Loans receivable | Residential | Residential mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans Outstanding, Individually evaluated for impairment			15,991
Loans Outstanding, Collectively evaluated for impairment			1,092,046
PCI Loans			9,579
Total	1,269,548		1,117,616
Allowance for credit losses, Individually evaluated for impairment			782
Allowance for credit losses, Collectively evaluated for impairment			7,296
Allowance for credit losses, PCI			3
Allowance for credit losses, Ending balance	17,562	12,826	8,081	8,214	8,290	8,295
Loans receivable | Residential | Home equity lines of credit
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans Outstanding, Individually evaluated for impairment			992
Loans Outstanding, Collectively evaluated for impairment			658,273
PCI Loans			1,410
Total	706,877		660,675
Allowance for credit losses, Individually evaluated for impairment			16
Allowance for credit losses, Collectively evaluated for impairment			4,541
Allowance for credit losses, PCI			18
Allowance for credit losses, Ending balance	8,721	8,687	4,575	4,683	4,794	4,752
Loans receivable | Consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans Outstanding, Individually evaluated for impairment			214
Loans Outstanding, Collectively evaluated for impairment			127,682
PCI Loans			336
Total	147,659		128,232
Allowance for credit losses, Individually evaluated for impairment			5
Allowance for credit losses, Collectively evaluated for impairment			885
Allowance for credit losses, PCI			11
Allowance for credit losses, Ending balance	$ 242	$ 460	$ 901	$ 877	$ 855	$ 853