Summary of Significant Accounting Policies (Details Textual) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 Age Branch Y Office	Dec. 31, 2011	Dec. 31, 2010
Summary of Significant Accounting Policies (Additional Textual) [Abstract]
Number of full-service branches	33
Number of loan production offices	8
Percentage value of estimated real estate	90.00%
Goodwill	$ 0	$ 0	$ 0
Recognized tax benefit	50.00%
Postretirement medical benefits number of years of service for eligibility	20
Postretirement medical benefits number of age of service for eligibility	60
Maximum [Member] | Buildings [Member]
Summary of Significant Accounting Policies (Textual) [Abstract]
Term of lease	40 years
Maximum [Member] | Furniture and Fixtures [Member]
Summary of Significant Accounting Policies (Textual) [Abstract]
Term of lease	5 years
Minimum [Member] | Buildings [Member]
Summary of Significant Accounting Policies (Textual) [Abstract]
Term of lease	20 years
Minimum [Member] | Furniture and Fixtures [Member]
Summary of Significant Accounting Policies (Textual) [Abstract]
Term of lease	3 years