Summary of Significant Accounting Policies - Premises and Equipment (Details)	12 Months Ended
	Dec. 31, 2012
Land Improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	10 years
Buildings | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	30 years
Buildings | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	40 years
Furniture and equipment | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	3 years
Furniture and equipment | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	10 years