Investment Securities (Amortized Cost of held To Maturity Debt Securities by Year of Originations and Credit Rating) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost, debt securities held-to-maturity	$ 445,444	$ 453,629
Total	445,531	453,629
AAA
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost, debt securities held-to-maturity	54,389	56,033
AA
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost, debt securities held-to-maturity	329,412	333,450
A
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost, debt securities held-to-maturity	59,837	62,652
BBB
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost, debt securities held-to-maturity	1,868	1,469
Not Rated
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost, debt securities held-to-maturity	25	25
Agency Obligations
Schedule of Held-to-maturity Securities [Line Items]
Total	7,417	6,599
Agency Obligations | AAA
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost, debt securities held-to-maturity	7,417	6,599
Agency Obligations | AA
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost, debt securities held-to-maturity	0	0
Agency Obligations | A
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost, debt securities held-to-maturity	0	0
Agency Obligations | BBB
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost, debt securities held-to-maturity	0	0
Agency Obligations | Not Rated
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost, debt securities held-to-maturity	0	0
Mortgage-Backed Securities
Schedule of Held-to-maturity Securities [Line Items]
Total	104	118
Mortgage-Backed Securities | AAA
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost, debt securities held-to-maturity	104	118
Mortgage-Backed Securities | AA
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost, debt securities held-to-maturity	0	0
Mortgage-Backed Securities | A
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost, debt securities held-to-maturity	0	0
Mortgage-Backed Securities | BBB
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost, debt securities held-to-maturity	0	0
Mortgage-Backed Securities | Not Rated
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost, debt securities held-to-maturity	0	0
State And Municipal Obligations
Schedule of Held-to-maturity Securities [Line Items]
Total	428,691	437,074
State And Municipal Obligations | AAA
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost, debt securities held-to-maturity	46,868	49,316
State And Municipal Obligations | AA
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost, debt securities held-to-maturity	326,291	330,322
State And Municipal Obligations | A
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost, debt securities held-to-maturity	54,414	56,317
State And Municipal Obligations | BBB
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost, debt securities held-to-maturity	1,118	1,119
State And Municipal Obligations | Not Rated
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost, debt securities held-to-maturity	0	0
Corporate Obligations
Schedule of Held-to-maturity Securities [Line Items]
Total	9,319	9,838
Corporate Obligations | AAA
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost, debt securities held-to-maturity	0	0
Corporate Obligations | AA
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost, debt securities held-to-maturity	3,121	3,128
Corporate Obligations | A
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost, debt securities held-to-maturity	5,423	6,335
Corporate Obligations | BBB
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost, debt securities held-to-maturity	750	350
Corporate Obligations | Not Rated
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost, debt securities held-to-maturity	$ 25	$ 25