Loans and Leases and Allowance for Credit Losses - Aging of recorded investment in past due loans (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Recorded investment in nonaccrual loans by loan class
Loans Outstanding, Ending Balance	$ 8,383,401	$ 7,735,572
Loans Receivable
Recorded investment in nonaccrual loans by loan class
Loans Past Due	38,304	36,929
Loans Not Past Due	8,270,648	7,600,129
PCI Loans	74,449	98,514
Loans Outstanding, Ending Balance	8,383,401	7,735,572
Loans Receivable | Loans Past Due, 30 - 59 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	22,405	21,010
Loans Receivable | Loans Past Due, 60 - 89 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	7,765	5,787
Loans Receivable | Loans Past Due, > 90 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	8,134	10,132
Loans Receivable | Home equity lines of credit
Recorded investment in nonaccrual loans by loan class
Loans Past Due	3,878	4,049
Loans Not Past Due	688,520	724,287
PCI Loans	1,612	2,891
Loans Outstanding, Ending Balance	694,010	731,227
Loans Receivable | Home equity lines of credit | Loans Past Due, 30 - 59 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	2,112	3,246
Loans Receivable | Home equity lines of credit | Loans Past Due, 60 - 89 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	864	225
Loans Receivable | Home equity lines of credit | Loans Past Due, > 90 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	902	578
Loans Receivable | Indirect auto
Recorded investment in nonaccrual loans by loan class
Loans Past Due	1,706	2,874
Loans Not Past Due	205,986	355,311
PCI Loans	0	0
Loans Outstanding, Ending Balance	207,692	358,185
Loans Receivable | Indirect auto | Loans Past Due, 30 - 59 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	750	1,152
Loans Receivable | Indirect auto | Loans Past Due, 60 - 89 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	323	459
Loans Receivable | Indirect auto | Loans Past Due, > 90 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	633	1,263
Loans Receivable | Commercial
Recorded investment in nonaccrual loans by loan class
Loans Past Due	22,056	16,161
Loans Not Past Due	6,014,967	5,265,034
PCI Loans	62,420	80,898
Loans Outstanding, Ending Balance	6,099,443	5,362,093
Loans Receivable | Commercial | Loans Past Due, 30 - 59 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	12,973	8,271
Loans Receivable | Commercial | Loans Past Due, 60 - 89 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	4,645	3,130
Loans Receivable | Commercial | Loans Past Due, > 90 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	4,438	4,760
Loans Receivable | Commercial | Owner occupied commercial real estate
Recorded investment in nonaccrual loans by loan class
Loans Past Due	6,450	7,116
Loans Not Past Due	1,631,602	1,891,118
PCI Loans	9,852	25,759
Loans Outstanding, Ending Balance	1,647,904	1,923,993
Loans Receivable | Commercial | Owner occupied commercial real estate | Loans Past Due, 30 - 59 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	2,542	3,810
Loans Receivable | Commercial | Owner occupied commercial real estate | Loans Past Due, 60 - 89 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	2,897	1,776
Loans Receivable | Commercial | Owner occupied commercial real estate | Loans Past Due, > 90 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	1,011	1,530
Loans Receivable | Commercial | Income producing commercial real estate
Recorded investment in nonaccrual loans by loan class
Loans Past Due	2,216	4,046
Loans Not Past Due	1,771,893	1,546,288
PCI Loans	38,311	44,840
Loans Outstanding, Ending Balance	1,812,420	1,595,174
Loans Receivable | Commercial | Income producing commercial real estate | Loans Past Due, 30 - 59 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	1,624	1,754
Loans Receivable | Commercial | Income producing commercial real estate | Loans Past Due, 60 - 89 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	291	353
Loans Receivable | Commercial | Income producing commercial real estate | Loans Past Due, > 90 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	301	1,939
Loans Receivable | Commercial | Construction
Recorded investment in nonaccrual loans by loan class
Loans Past Due	335	858
Loans Not Past Due	789,916	702,221
PCI Loans	5,907	8,857
Loans Outstanding, Ending Balance	796,158	711,936
Loans Receivable | Commercial | Construction | Loans Past Due, 30 - 59 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	267	568
Loans Receivable | Commercial | Construction | Loans Past Due, 60 - 89 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	0	132
Loans Receivable | Commercial | Construction | Loans Past Due, > 90 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	68	158
Loans Receivable | Commercial | Equipment financing
Recorded investment in nonaccrual loans by loan class
Loans Past Due	4,748	0
Loans Not Past Due	551,924	0
PCI Loans	7,942	0
Loans Outstanding, Ending Balance	564,614	0
Loans Receivable | Commercial | Equipment financing | Loans Past Due, 30 - 59 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	1,351	0
Loans Receivable | Commercial | Equipment financing | Loans Past Due, 60 - 89 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	739	0
Loans Receivable | Commercial | Equipment financing | Loans Past Due, > 90 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	2,658	0
Loans Receivable | Residential | Construction
Recorded investment in nonaccrual loans by loan class
Loans Past Due	762	1,083
Loans Not Past Due	209,515	181,472
PCI Loans	734	464
Loans Outstanding, Ending Balance	211,011	183,019
Loans Receivable | Residential | Construction | Loans Past Due, 30 - 59 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	509	885
Loans Receivable | Residential | Construction | Loans Past Due, 60 - 89 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	63	105
Loans Receivable | Residential | Construction | Loans Past Due, > 90 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	190	93
Loans Receivable | Residential | Residential mortgage
Recorded investment in nonaccrual loans by loan class
Loans Past Due	9,199	11,890
Loans Not Past Due	1,030,883	948,513
PCI Loans	9,150	13,141
Loans Outstanding, Ending Balance	1,049,232	973,544
Loans Receivable | Residential | Residential mortgage | Loans Past Due, 30 - 59 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	5,461	6,717
Loans Receivable | Residential | Residential mortgage | Loans Past Due, 60 - 89 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	1,788	1,735
Loans Receivable | Residential | Residential mortgage | Loans Past Due, > 90 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	1,950	3,438
Loans Receivable | Consumer direct
Recorded investment in nonaccrual loans by loan class
Loans Past Due	703	872
Loans Not Past Due	120,777	125,512
PCI Loans	533	1,120
Loans Outstanding, Ending Balance	122,013	127,504
Loans Receivable | Consumer direct | Loans Past Due, 30 - 59 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	600	739
Loans Receivable | Consumer direct | Loans Past Due, 60 - 89 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	82	133
Loans Receivable | Consumer direct | Loans Past Due, > 90 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	21	0
Loans Receivable | Commercial & industrial | Commercial
Recorded investment in nonaccrual loans by loan class
Loans Past Due	8,307	4,141
Loans Not Past Due	1,269,632	1,125,407
PCI Loans	408	1,442
Loans Outstanding, Ending Balance	1,278,347	1,130,990
Loans Receivable | Commercial & industrial | Commercial | Loans Past Due, 30 - 59 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	7,189	2,139
Loans Receivable | Commercial & industrial | Commercial | Loans Past Due, 60 - 89 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	718	869
Loans Receivable | Commercial & industrial | Commercial | Loans Past Due, > 90 Days
Recorded investment in nonaccrual loans by loan class
Loans Past Due	$ 400	$ 1,133