Allowance for Loan Losses and Credit Quality of Loans, Allowance for Loan Losses by Portfolio Segments (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Changes in allowance for loan losses by portfolio segment [Roll Forward]
Balance, beginning of period	$ 72,505	$ 69,500
Charge-offs	(8,454)	(8,674)
Recoveries	1,547	1,878
Provision	5,807	7,496
Balance, end of period	71,405	70,200
Commercial Loans [Member]
Changes in allowance for loan losses by portfolio segment [Roll Forward]
Balance, beginning of period	32,759	27,606
Charge-offs	(747)	(805)
Recoveries	94	187
Provision	53	1,202
Balance, end of period	32,159	28,190
Consumer Loans [Member]
Changes in allowance for loan losses by portfolio segment [Roll Forward]
Balance, beginning of period	37,178	36,830
Charge-offs	(7,433)	(7,687)
Recoveries	1,399	1,644
Provision	5,660	6,186
Balance, end of period	36,804	36,973
Residential Real Estate [Member]
Changes in allowance for loan losses by portfolio segment [Roll Forward]
Balance, beginning of period	2,568	5,064
Charge-offs	(274)	(182)
Recoveries	54	47
Provision	94	108
Balance, end of period	2,442	5,037
Acquired Loans [Member]
Changes in allowance for loan losses by portfolio segment [Roll Forward]
Balance, beginning of period	0
Charge-offs	0	$ 100
Balance, end of period	$ 0

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- Definition

Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

+ References

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-Publisher FASB
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- Definition

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.

+ References

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- Definition

Amount of expense related to estimated loss from loan and lease transactions.

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