Allowance for Credit Losses and Credit Quality of Loans, Allowance for Credit Losses on Off-Balance Sheet Credit Exposures (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Jun. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Allowance for Credit Losses and Credit Quality of Loans [Abstract]
Allowance for credit losses	$ 93,000	$ 98,500	$ 110,000	$ 114,500	$ 113,500	$ 75,999
Unfunded Commitment [Member]
Allowance for Credit Losses and Credit Quality of Loans [Abstract]
Allowance for credit losses	$ 5,300		$ 6,400