Shareholders' Equity (Regulatory Captial Requirements) (Details) - USD ($) $ in Thousands		Sep. 30, 2019	Dec. 31, 2018
Corporation [Member]
Total Capital (to Risk-Weighted Assets):
Total Capital		$ 486,454	$ 455,699
Total Capital to Risk-Weighted Assets		12.94%	12.56%
Total Capital for Capital Adequacy Purposes		$ 300,835	$ 290,146
Total Capital for Capital Adequacy Purposes to Risk-Weighted Assets		8.00%	8.00%
Tier 1 Capital (to Risk-Weighted Assets):
Tier 1 Capital		$ 459,140	$ 428,338
Tier 1 Capital to Risk Weighted-Assets		12.21%	11.81%
Tier 1 Capital Required For Capital Adequacy Purposes		$ 225,627	$ 217,609
Tier 1 Capital Required for Capital Adequacy Purposes to Risk Weighted-Assets		6.00%	6.00%
Common Equity Tier 1 Capital [Abstract]
Common Equity Tier 1 Capital		$ 437,142	$ 406,340
Common Equity Tier 1 Capital to Risk Weighted Assets		11.62%	11.20%
Common Equity Tier 1 Capital Required for Capital Adequacy		$ 169,220	$ 163,207
Common Equity Tier 1 Capital for Capital Adequacy to Risk Weighted Assets		4.50%	4.50%
Tier 1 Capital (to Average Assets):
Tier 1 Leverage Capital	[1]	$ 459,140	$ 428,338
Tier 1 Leverage Capital to Average Assets	[1]	8.97%	8.89%
Tier 1 Leverage Capital Required for Capital Adequacy Purposes	[1]	$ 204,810	$ 192,690
Tier 1 Leverage Capital Required for Capital Adequacy Purposes to Average Assets	[1]	4.00%	4.00%
Bank [Member]
Total Capital (to Risk-Weighted Assets):
Total Capital		$ 483,783	$ 453,033
Total Capital to Risk-Weighted Assets		12.87%	12.49%
Total Capital for Capital Adequacy Purposes		$ 300,790	$ 290,128
Total Capital for Capital Adequacy Purposes to Risk-Weighted Assets		8.00%	8.00%
Total Capital To Be Well Capitalized		$ 375,988	$ 362,660
Total Capital To Be Well Capitalized to Risk Weighted-Assets		10.00%	10.00%
Tier 1 Capital (to Risk-Weighted Assets):
Tier 1 Capital		$ 456,469	$ 425,672
Tier 1 Capital to Risk Weighted-Assets		12.14%	11.74%
Tier 1 Capital Required For Capital Adequacy Purposes		$ 225,593	$ 217,596
Tier 1 Capital Required for Capital Adequacy Purposes to Risk Weighted-Assets		6.00%	6.00%
Tier 1 Capital Required To Be Well Capitalized		$ 300,790	$ 290,128
Tier 1 Capital Required To Be Well Capitalized to Risk Weighted-Assets		8.00%	8.00%
Common Equity Tier 1 Capital [Abstract]
Common Equity Tier 1 Capital		$ 456,469	$ 425,672
Common Equity Tier 1 Capital to Risk Weighted Assets		12.14%	11.74%
Common Equity Tier 1 Capital Required for Capital Adequacy		$ 169,195	$ 163,197
Common Equity Tier 1 Capital for Capital Adequacy to Risk Weighted Assets		4.50%	4.50%
Common Equity Tier 1 Capital Required to be Well Capitalized		$ 244,392	$ 235,729
Common Equity Tier 1 Capital Required to be Well Capitalized to Risk Weighted Assets		6.50%	6.50%
Tier 1 Capital (to Average Assets):
Tier 1 Leverage Capital	[1]	$ 456,469	$ 425,672
Tier 1 Leverage Capital to Average Assets	[1]	8.92%	8.84%
Tier 1 Leverage Capital Required for Capital Adequacy Purposes	[1]	$ 204,722	$ 192,652
Tier 1 Leverage Capital Required for Capital Adequacy Purposes to Average Assets	[1]	4.00%	4.00%
Tier 1 Leverage Capital Required To Be Well Capitalized	[1]	$ 255,903	$ 240,815
Tier 1 Leverage Capital Required To Be Well Capitalized to Average Assets	[1]	5.00%	5.00%

[1] Leverage ratio.