Allowance for Loan and Lease Losses - Activity (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) class segment	Sep. 30, 2018 USD ($)
Allowance for loan and lease losses
Number of primary portfolio segments | segment			3
Allowance for loan and lease losses:
Balance at beginning of period	$ 138,535,000	$ 140,601,000	$ 141,718,000	$ 137,253,000
Charge-offs	(8,536,000)	(6,128,000)	(26,663,000)	(19,552,000)
Recoveries	2,965,000	2,317,000	8,359,000	7,119,000
Increase (decrease) in Provision		4,460,000	9,550,000	16,430,000
Balance at end of period	132,964,000	141,250,000	$ 132,964,000	141,250,000
Commercial Lending
Allowance for loan and lease losses
Number of distinct portfolios | class			4
Commercial and Industrial
Allowance for loan and lease losses:
Balance at beginning of period	31,688,000	35,239,000	$ 34,501,000	34,006,000
Charge-offs	(514,000)	(303,000)	(2,514,000)	(778,000)
Recoveries	241,000	51,000	303,000	154,000
Increase (decrease) in Provision	(4,098,000)	(1,551,000)	(4,973,000)	54,000
Balance at end of period	27,317,000	33,436,000	27,317,000	33,436,000
Commercial real estate
Allowance for loan and lease losses:
Balance at beginning of period	22,204,000	20,507,000	19,725,000	18,044,000
Recoveries	30,000	21,000	93,000	175,000
Increase (decrease) in Provision	(358,000)	286,000	2,058,000	2,595,000
Balance at end of period	21,876,000	20,814,000	21,876,000	20,814,000
Construction
Allowance for loan and lease losses:
Balance at beginning of period	5,014,000	7,606,000	5,813,000	6,817,000
Increase (decrease) in Provision	(361,000)	(1,388,000)	(1,160,000)	(599,000)
Balance at end of period	4,653,000	6,218,000	4,653,000	6,218,000
Lease financing
Allowance for loan and lease losses:
Balance at beginning of period	446,000	557,000	432,000	611,000
Charge-offs			(24,000)
Increase (decrease) in Provision	(54,000)	(29,000)	(16,000)	(83,000)
Balance at end of period	392,000	528,000	392,000	528,000
Residential mortgage
Allowance for loan and lease losses
Specific allocation for impaired loans in which the net collateral value exceeds the unpaid principal balance of the loan	0		0
Allowance for loan and lease losses:
Balance at beginning of period	43,420,000	43,925,000	44,906,000	42,852,000
Charge-offs	(7,000)	(125,000)	(7,000)	(159,000)
Recoveries	425,000	442,000	860,000	684,000
Increase (decrease) in Provision	241,000	147,000	(1,680,000)	1,012,000
Balance at end of period	44,079,000	44,389,000	44,079,000	44,389,000
Consumer
Allowance for loan and lease losses:
Balance at beginning of period	33,638,000	31,509,000	35,813,000	31,249,000
Charge-offs	(8,015,000)	(5,700,000)	(24,118,000)	(18,615,000)
Recoveries	2,269,000	1,803,000	7,103,000	6,106,000
Increase (decrease) in Provision	5,838,000	6,381,000	14,932,000	15,253,000
Balance at end of period	33,730,000	33,993,000	33,730,000	33,993,000
Unallocated
Allowance for loan and lease losses:
Balance at beginning of period	2,125,000	1,258,000	528,000	3,674,000
Increase (decrease) in Provision	(1,208,000)	614,000	389,000	(1,802,000)
Balance at end of period	$ 917,000	$ 1,872,000	$ 917,000	$ 1,872,000