Loans (Narrative) (Details) $ in Thousands		Dec. 31, 2020 USD ($) loan	Dec. 31, 2019 USD ($)
Receivables [Abstract]
Carrying value of Payment Protection Program loans		$ 199,800
Net unamortized loan origination costs		1,500	$ 5,300
Net unamortized premiums on purchased loans		787	995
Accrued interest receivable		11,300	11,000
Loans pledged as collateral		$ 2,100,000	2,100,000
Number of executed loan modifications due to COVID-19 | loan		636
Balance of executed loan modifications due to COVID-19		$ 717,400
Number of active deferments due to COVID-19 | loan		136
Balance of active deferments due to COVID-19		$ 244,700
Nonaccrual loans		8,500	11,500
Nonaccrual loans, no ACL deemed necessary		3,000
Residential loans in process of foreclosure		3,400	5,800
Nonaccrual loans current on payment		4,700	5,900
Individually analyzed loans		18,300
Total loans	[1]	4,195,990	3,892,999
Total loans	[1]	4,195,990	$ 3,892,999
Collateral Dependent Individually Analyzed [Member]
Receivables [Abstract]
Total loans		8,444
Total loans		$ 8,444

[1] Includes net unamortized loan origination costs of $1.5 million and $5.3 million, respectively, at December 31, 2020 and 2019 and net unamortized premiums on purchased loans of $787 thousand and $995 thousand, respectively, at December 31, 2020 and 2019.