Securities Securities (Reconciliation of amortized cost of held to maturity securities) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	$ 805,529	$ 724,512
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	21,311	28,007
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(6,410)	(342)
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0	0
Debt Securities, Held-to-maturity, Fair Value	820,430	752,177
Small Business Administration Pooled Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	26,518	26,917
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	717	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	27,235	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	355,686	335,993
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	7,474	8,466
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(2,158)	(340)
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0	0
Debt Securities, Held-to-maturity, Fair Value	361,002	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	417,811	356,085
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	13,069	18,036
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(4,252)	0
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0	0
Debt Securities, Held-to-maturity, Fair Value	426,628	374,121
US Treasury Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	4,014	4,017
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	43	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	$ 4,057	$ 4,077