Allowance for Loan Losses and Credit Quality of Loans, Allowance for Loan Losses by Portfolio Segments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Changes in allowance for loan losses by portfolio segment [Roll Forward]
Balance, beginning of period	$ 72,505	$ 69,500	$ 65,200
Charge-offs	(32,540)	(34,128)	(33,087)
Recoveries	7,588	8,305	6,399
Provision	25,412	28,828	30,988
Balance, end of period	72,965	72,505	69,500
Commercial Loans [Member]
Changes in allowance for loan losses by portfolio segment [Roll Forward]
Balance, beginning of period	32,759	27,606	25,444
Charge-offs	(3,151)	(3,463)	(4,169)
Recoveries	534	1,178	1,077
Provision	4,383	7,438	5,254
Balance, end of period	34,525	32,759	27,606
Consumer Loans [Member]
Changes in allowance for loan losses by portfolio segment [Roll Forward]
Balance, beginning of period	37,178	36,830	33,375
Charge-offs	(28,398)	(29,752)	(27,072)
Recoveries	6,913	6,821	5,142
Provision	19,954	23,279	25,385
Balance, end of period	35,647	37,178	36,830
Residential Real Estate [Member]
Changes in allowance for loan losses by portfolio segment [Roll Forward]
Balance, beginning of period	2,568	5,064	6,381
Charge-offs	(991)	(913)	(1,846)
Recoveries	141	306	180
Provision	1,075	(1,889)	349
Balance, end of period	2,793	2,568	5,064
Acquired Loans [Member]
Changes in allowance for loan losses by portfolio segment [Roll Forward]
Balance, beginning of period	0
Charge-offs	(100)	(100)	$ (700)
Balance, end of period	$ 0	$ 0