Summary of Significant Accounting Policies (Details 2) (Loans, Concentrations of Credit Risk, USD $) In Millions, unless otherwise specified	Dec. 31, 2012 item
Concentrations of Credit Risk
Concentration risk threshold, total risk-based capital threshold (as a percent)	25.00%
Concentration risk threshold, total risk-based capital threshold	$ 119.1
Number of credit concentrations for non-acquired loans	5
Borrowers engaged in other activities related to real estate
Concentrations of Credit Risk
Amount loaned	258.2
Lessors of residential buildings
Concentrations of Credit Risk
Amount loaned	142.7
Lessors of nonresidential buildings
Concentrations of Credit Risk
Amount loaned	160.8
Other holding companies
Concentrations of Credit Risk
Amount loaned	158.2
Religious
Concentrations of Credit Risk
Amount loaned	$ 162.8