Allowance for Credit Losses and Credit Quality of Loans, Changes in Allowance for Loan Losses by Portfolio Segment (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Changes in allowance for loan losses by portfolio segment [Roll Forward]
Balance, beginning of period		$ 72,965	[1]	$ 72,505		$ 69,500
Charge-offs				(32,540)		(34,128)
Recoveries				7,588		8,305
Provision	[1]	51,134		25,412		28,828
Balance, end of period				72,965	[1]	72,505
Commercial Loans [Member]
Changes in allowance for loan losses by portfolio segment [Roll Forward]
Balance, beginning of period		34,525		32,759		27,606
Charge-offs				(3,151)		(3,463)
Recoveries				534		1,178
Provision				4,383		7,438
Balance, end of period				34,525		32,759
Consumer Loans [Member]
Changes in allowance for loan losses by portfolio segment [Roll Forward]
Balance, beginning of period		35,647		37,178		36,830
Charge-offs				(28,398)		(29,752)
Recoveries				6,913		6,821
Provision				19,954		23,279
Balance, end of period				35,647		37,178
Residential Real Estate [Member]
Changes in allowance for loan losses by portfolio segment [Roll Forward]
Balance, beginning of period		$ 2,793		2,568		5,064
Charge-offs				(991)		(913)
Recoveries				141		306
Provision				1,075		(1,889)
Balance, end of period				$ 2,793		$ 2,568

[1] Beginning January 1, 2020, calculation is based on current expected loss methodology. Prior to January 1, 2020, calculation was based on incurred loss methodology.