Investment Securities (Narrative) (Details) - USD ($)	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Schedule of Investments [Line Items]
Other than Temporary Impairment Losses, Investments	$ 0	$ 0
Debt Securities, Available-for-sale, Amortized Cost	1,747,396,000		$ 1,854,852,000
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	$ 0
Debt Securities, Available-for-sale	1,609,156,000		1,733,696,000
Debt Securities, Available-for-sale, Unrealized Loss Position	1,592,003,000		1,590,490,000
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	138,257,000		122,776,000
Securities Available-for-Sale, 12 months or longer, Fair value	1,303,558,000		413,070,000
U.S. Government Sponsored Entities Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	735,317,000		839,399,000
Debt Securities, Available-for-sale	640,282,000		756,761,000
Debt Securities, Available-for-sale, Unrealized Loss Position	640,282,000		756,761,000
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	95,035,000		82,638,000
Securities Available-for-Sale, 12 months or longer, Fair value	639,111,000		310,338,000
USGovernmentSponsored asset backed securities and US Treasury obligations
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	96,700,000
Collateral Pledged [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Restricted	$ 606,200,000		$ 753,600,000