Impact of Recent Accounting Pronouncements (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Jun. 30, 2020	Mar. 31, 2020	Jan. 01, 2020	Jun. 30, 2019	Mar. 31, 2019
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Allowance for credit losses	$ 55,525	$ 55,562	$ 86,259	$ 75,143	$ 55,525	$ 62,810	$ 55,353
Accounting standards update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member	us-gaap:AccountingStandardsUpdate201602Member
Provision for credit losses for off-balance sheet credit exposure					0
Retained earnings	$ 695,273		$ 685,509
Cumulative Effect, Period of Adoption, Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Allowance for credit losses					7,920
Provision for credit losses for off-balance sheet credit exposure					3,206
Retained earnings					8,300
Cumulative Effect, Period of Adoption, Adjustment | Construction
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Allowance for credit losses					$ 1,300