Securities Securities (Reconciliation of amortized cost of held to maturity securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	$ 865,249	$ 724,512
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	17,167	28,007
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(7,110)	(342)
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0	0
Debt Securities, Held-to-maturity, Fair Value	875,306	752,177
Small Business Administration Pooled Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	23,686	26,917
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	1,142	1,445
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	0
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0	0
Debt Securities, Held-to-maturity, Fair Value	24,828	28,362
Trust Preferred Securities Subject to Mandatory Redemption [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	1,500	1,500
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	8	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	(2)
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0	0
Debt Securities, Held-to-maturity, Fair Value	1,508	1,498
Collateralized Debt Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	451,151	335,993
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	5,089	8,466
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(4,202)	(340)
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0	0
Debt Securities, Held-to-maturity, Fair Value	452,038	344,119
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	352,483	356,085
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	10,911	18,036
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(2,781)	0
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0	0
Debt Securities, Held-to-maturity, Fair Value	360,613	374,121
US Treasury Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	3,007	4,017
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	17	60
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	0
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0	0
Debt Securities, Held-to-maturity, Fair Value	3,024	4,077
U.S. government agency securities
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	33,422	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(127)	0
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0	0
Debt Securities, Held-to-maturity, Fair Value	$ 33,295	$ 0