Goodwill, Core Deposit Premium and Other Intangible Assets (Mortgage loans servicing) (Details) (USD $)					6 Months Ended	12 Months Ended	6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2013 Mortgage Servicing Rights 15-year Tranche [Member]	Dec. 31, 2012 Mortgage Servicing Rights 15-year Tranche [Member]	Jun. 30, 2013 Mortgage Servicing Rights 30-year Tranche [Member]	Dec. 31, 2012 Mortgage Servicing Rights 30-year Tranche [Member]	Jun. 30, 2013 GNMA [Member]
Goodwill and Intangible Assets Disclosure [Abstract]
Mortgage loans serviced for others	$ 2,700,000,000	$ 2,200,000,000
Valuation allowance	0	496,000
Valuation servicing rights in tranches [Line Items]
Servicing asset at amortized value	24,600,000	16,000,000			4,200,000	3,300,000	18,800,000	12,600,000	1,600,000
Servicing asset, agreement term					15 years	15 years	30 years
Servicing asset at amortized cost	$ 19,621,000	$ 15,653,000	$ 12,864,000	$ 11,276,000	$ 3,200,000	$ 3,000,000	$ 15,300,000	$ 12,600,000	$ 1,100,000