Regulatory Capital Requirements (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Total risk-based capital:
Actual Regulatory Capital - Amount	$ 239,831	$ 232,339
Minimum Regulatory Capital Required - Amount	123,293	116,567
Actual Regulatory Capital - Amount	154,116	145,709
Capital To Risk Weighted Assets	15.56%	15.95%
Minimum Regulatory Capital Required - Ratio	8.00%	8.00%
Minimum Regulatory Provision To Be Well Capitalized - Ratio	10.00%	10.00%
Tier 1 capital:
Actual Regulatory Capital - Amount	220,519	214,066
Minimum Regulatory Capital Required - Amount	61,646	58,284
Minimum Regulatory Provision To Be Well Capitalized - Amount	92,469	87,426
Actual Regulatory Capital - Ratio	14.31%	14.69%
Minimum Regulatory Capital Required - Ratio	4.00%	4.00%
Minimum Regulatory Provision To Be Well Capitalized - Ratio	6.00%	6.00%
Tier 1 leverage capital ratio:
Actual Regulatory Capital - Amount	220,519	214,066
Minimum Regulatory Capital Required - Amount	100,770	91,056
Minimum Regulatory Provision To Be Well Capitalized - Amount	125,963	113,820
Actual Regulatory Capital - Ratio	8.94%	9.59%
Minimum Regulatory Capital Required - Ratio	4.00%	4.00%
Minimum Regulatory Provision To Be Well Capitalized - Ratio	5.00%	5.00%
Subsidiaries [Member]
Total risk-based capital:
Actual Regulatory Capital - Amount	213,435	208,580
Minimum Regulatory Capital Required - Amount	121,625	115,074
Actual Regulatory Capital - Amount	152,031	143,842
Capital To Risk Weighted Assets	14.04%	14.50%
Minimum Regulatory Capital Required - Ratio	8.00%	8.00%
Minimum Regulatory Provision To Be Well Capitalized - Ratio	10.00%	10.00%
Tier 1 capital:
Actual Regulatory Capital - Amount	194,381	190,538
Minimum Regulatory Capital Required - Amount	60,812	57,537
Minimum Regulatory Provision To Be Well Capitalized - Amount	91,219	86,305
Actual Regulatory Capital - Ratio	12.79%	13.25%
Minimum Regulatory Capital Required - Ratio	4.00%	4.00%
Minimum Regulatory Provision To Be Well Capitalized - Ratio	6.00%	6.00%
Tier 1 leverage capital ratio:
Actual Regulatory Capital - Amount	194,381	190,538
Minimum Regulatory Capital Required - Amount	99,347	89,836
Minimum Regulatory Provision To Be Well Capitalized - Amount	$ 124,184	$ 112,295
Actual Regulatory Capital - Ratio	7.97%	8.63%
Minimum Regulatory Capital Required - Ratio	4.00%	4.00%
Minimum Regulatory Provision To Be Well Capitalized - Ratio	5.00%	5.00%