Shareholders' Equity (Regulatory Captial Requirements) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Corporation [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital	$ 309,170		$ 304,716
Total Capital to Risk-Weighted Assets	13.50%		13.26%
Total Capital for Capital Adequacy Purposes	183,224		183,876
Total Capital for Capital Adequacy Purposes to Risk-Weighted Assets	8.00%		8.00%
Total Capital To Be Well Capitalized	229,030		229,845
Total Capital To Be Well Capitalized to Risk Weighted-Assets	10.00%		10.00%
Tier 1 Capital	280,507		275,956
Tier 1 Capital to Risk Weighted-Assets	12.25%		12.01%
Tier 1 Capital Required For Capital Adequacy Purposes	91,612		91,938
Tier 1 Capital Required for Capital Adequacy Purposes to Risk Weighted-Assets	4.00%		4.00%
Tier 1 Capital Required To Be Well Capitalized	137,418		137,907
Tier 1 Capital Required To Be Well Capitalized to Risk Weighted-Assets	6.00%		6.00%
Tier 1 Leverage Capital	280,507	[1]	275,956	[1]
Tier 1 Leverage Capital to Average Assets	9.53%	[1]	9.30%	[1]
Tier 1 Leverage Capital Required for Capital Adequacy Purposes	117,760	[1]	118,733	[1]
Tier 1 Leverage Capital Required for Capital Adequacy Purposes to Average Assets	4.00%	[1]	4.00%	[1]
Tier 1 Leverage Capital Required To Be Well Capitalized	147,200	[1]	148,417	[1]
Tier 1 Leverage Capital Required To Be Well Capitalized to Average Assets	5.00%	[1]	5.00%	[1]
Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital	303,533		299,503
Total Capital to Risk-Weighted Assets	13.27%		13.05%
Total Capital for Capital Adequacy Purposes	183,002		183,651
Total Capital for Capital Adequacy Purposes to Risk-Weighted Assets	8.00%		8.00%
Total Capital To Be Well Capitalized	228,752		229,564
Total Capital To Be Well Capitalized to Risk Weighted-Assets	10.00%		10.00%
Tier 1 Capital	274,904		270,778
Tier 1 Capital to Risk Weighted-Assets	12.02%		11.80%
Tier 1 Capital Required For Capital Adequacy Purposes	91,501		91,826
Tier 1 Capital Required for Capital Adequacy Purposes to Risk Weighted-Assets	4.00%		4.00%
Tier 1 Capital Required To Be Well Capitalized	137,251		137,738
Tier 1 Capital Required To Be Well Capitalized to Risk Weighted-Assets	6.00%		6.00%
Tier 1 Leverage Capital	274,904	[1]	270,778	[1]
Tier 1 Leverage Capital to Average Assets	9.35%	[1]	9.14%	[1]
Tier 1 Leverage Capital Required for Capital Adequacy Purposes	117,552	[1]	118,535	[1]
Tier 1 Leverage Capital Required for Capital Adequacy Purposes to Average Assets	4.00%	[1]	4.00%	[1]
Tier 1 Leverage Capital Required To Be Well Capitalized	$ 146,940	[1]	$ 148,169	[1]
Tier 1 Leverage Capital Required To Be Well Capitalized to Average Assets	5.00%	[1]	5.00%	[1]

[1] Leverage ratio