Investment Securities (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Schedule of Investments [Line Items]
Other than Temporary Impairment Losses, Investments			$ 0	$ 0
Debt Securities, Available-for-sale, Amortized Cost	$ 1,363,823		1,363,823		$ 1,007,834
Debt Securities, Available-for-sale, Allowance for Credit Loss	0		$ 0
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			21.00%
Debt Securities, Available for Sale, Sold at Gain, Amortized Cost Amount			$ 0	55,500
Debt Securities, Realized Gain (Loss)	0	$ 3,313	0	$ 3,313
U.S. Government Sponsored Entities Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	856,255		856,255		726,589
Collateral Pledged [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Restricted	$ 710,000		$ 710,000		$ 691,000