Shareholders' Equity (Regulatory Captial Requirements) (Details) - USD ($) $ in Thousands		Mar. 31, 2019	Dec. 31, 2018
Corporation [Member]
Total Capital (to Risk-Weighted Assets):
Total Capital		$ 467,260	$ 455,699
Total Capital to Risk-Weighted Assets		12.59%	12.56%
Total Capital for Capital Adequacy Purposes		$ 296,925	$ 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		$ 439,374	$ 428,338
Tier 1 Capital to Risk Weighted-Assets		11.84%	11.81%
Tier 1 Capital Required For Capital Adequacy Purposes		$ 222,694	$ 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		$ 417,376	$ 406,340
Common Equity Tier 1 Capital to Risk Weighted Assets		11.25%	11.20%
Common Equity Tier 1 Capital Required for Capital Adequacy		$ 167,020	$ 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]	$ 439,374	$ 428,338
Tier 1 Leverage Capital to Average Assets	[1]	8.69%	8.89%
Tier 1 Leverage Capital Required for Capital Adequacy Purposes	[1]	$ 202,274	$ 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		$ 463,549	$ 453,033
Total Capital to Risk-Weighted Assets		12.49%	12.49%
Total Capital for Capital Adequacy Purposes		$ 296,892	$ 290,128
Total Capital for Capital Adequacy Purposes to Risk-Weighted Assets		8.00%	8.00%
Total Capital To Be Well Capitalized		$ 371,115	$ 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		$ 435,663	$ 425,672
Tier 1 Capital to Risk Weighted-Assets		11.74%	11.74%
Tier 1 Capital Required For Capital Adequacy Purposes		$ 222,669	$ 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		$ 296,892	$ 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		$ 435,663	$ 425,672
Common Equity Tier 1 Capital to Risk Weighted Assets		11.74%	11.74%
Common Equity Tier 1 Capital Required for Capital Adequacy		$ 167,002	$ 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		$ 241,225	$ 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]	$ 435,663	$ 425,672
Tier 1 Leverage Capital to Average Assets	[1]	8.62%	8.84%
Tier 1 Leverage Capital Required for Capital Adequacy Purposes	[1]	$ 202,213	$ 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]	$ 252,767	$ 240,815
Tier 1 Leverage Capital Required To Be Well Capitalized to Average Assets	[1]	5.00%	5.00%

[1] Leverage ratio.