The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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The balance of financing receivables that were collectively evaluated for impairment.

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The balance of financing receivables that were individually evaluated for impairment.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Allowance for Loan Losses Allowance by Impairment Analysis Method (Details) - USD ($)	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment Recorded investment (loan balance)	$ 25,649,000	$ 19,187,000
Individually Evaluated for Impairment Allowance for loan losses	259,000	235,000
Collectively Evaluated for Impairment Recorded investment (loan balance)	7,017,689,000	6,957,517,000
Collectively Evaluated for Impairment Allowance for loan losses	67,952,000	71,747,000
Total Loans Receivable	7,043,338,000	6,976,704,000
Allowance for loan losses	68,211,000	71,982,000	$ 73,814,000	$ 75,312,000
Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment Recorded investment (loan balance)	828,000
Individually Evaluated for Impairment Allowance for loan losses	175,000
Collectively Evaluated for Impairment Recorded investment (loan balance)	669,916,000
Collectively Evaluated for Impairment Allowance for loan losses	10,080,000
Total Loans Receivable	670,744,000
Allowance for loan losses	10,255,000	10,048,000	15,687,000	15,912,000
Commercial and industrial, including tax exempt
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment Recorded investment (loan balance)		724,000
Individually Evaluated for Impairment Allowance for loan losses		146,000
Collectively Evaluated for Impairment Recorded investment (loan balance)		1,141,237,000
Collectively Evaluated for Impairment Allowance for loan losses		15,918,000
Total Loans Receivable		1,141,961,000
Allowance for loan losses		16,064,000
Commercial tax-exempt
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment Recorded investment (loan balance)	0
Individually Evaluated for Impairment Allowance for loan losses	0
Collectively Evaluated for Impairment Recorded investment (loan balance)	445,319,000
Collectively Evaluated for Impairment Allowance for loan losses	1,927,000
Total Loans Receivable	445,319,000
Allowance for loan losses	1,927,000	6,016,000
Commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment Recorded investment (loan balance)	6,119,000	733,000
Individually Evaluated for Impairment Allowance for loan losses	0	0
Collectively Evaluated for Impairment Recorded investment (loan balance)	2,620,180,000	2,550,541,000
Collectively Evaluated for Impairment Allowance for loan losses	36,580,000	40,765,000
Total Loans Receivable	2,626,299,000	2,551,274,000
Allowance for loan losses	36,580,000	40,765,000	41,813,000	41,934,000
Construction and land
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment Recorded investment (loan balance)	0	0
Individually Evaluated for Impairment Allowance for loan losses	0	0
Collectively Evaluated for Impairment Recorded investment (loan balance)	238,293,000	225,983,000
Collectively Evaluated for Impairment Allowance for loan losses	5,709,000	5,119,000
Total Loans Receivable	238,293,000	225,983,000
Allowance for loan losses	5,709,000	5,119,000	5,353,000	6,022,000
Residential
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment Recorded investment (loan balance)	16,884,000	15,900,000
Individually Evaluated for Impairment Allowance for loan losses	64,000	67,000
Collectively Evaluated for Impairment Recorded investment (loan balance)	2,825,042,000	2,823,255,000
Collectively Evaluated for Impairment Allowance for loan losses	11,715,000	8,790,000
Total Loans Receivable	2,841,926,000	2,839,155,000
Allowance for loan losses	11,779,000	8,857,000	10,057,000	10,026,000
Home equity
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment Recorded investment (loan balance)	1,818,000	1,830,000
Individually Evaluated for Impairment Allowance for loan losses	20,000	22,000
Collectively Evaluated for Impairment Recorded investment (loan balance)	87,532,000	81,827,000
Collectively Evaluated for Impairment Allowance for loan losses	283,000	756,000
Total Loans Receivable	89,350,000	83,657,000
Allowance for loan losses	303,000	778,000	796,000	1,284,000
Consumer and other
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment Recorded investment (loan balance)	0	0
Individually Evaluated for Impairment Allowance for loan losses	0	0
Collectively Evaluated for Impairment Recorded investment (loan balance)	131,407,000	134,674,000
Collectively Evaluated for Impairment Allowance for loan losses	1,658,000	399,000
Total Loans Receivable	131,407,000	134,674,000
Allowance for loan losses	1,658,000	399,000	$ 108,000	$ 134,000
Financial Asset Acquired with Credit Deterioration
Financing Receivable, Allowance for Credit Loss [Line Items]
Total Loans Receivable	$ 0	$ 0