Mortgage Servicing Rights (Details 2) (Mortgage Servicing Rights., USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Mortgage Servicing Rights.
Change in Carrying Value of Mortgage Servicing Rights Accounted for Under the Amortization Method, Net of a Valuation Allowance
Balance at the beginning of the Period	$ 17,148	$ 15,153	$ 10,638
Servicing Rights that Resulted From Asset Transfers	6,016	4,139	6,086
Amortization	(2,685)	(2,144)	(1,571)
Balance at the end of the Period	20,479	17,148	15,153
Fair Value of Mortgage Servicing Rights Accounted for Under the Amortization Method
Balance at the beginning of the Period	17,159	20,340	14,853
Balance at the end of the Period	$ 23,143	$ 17,159	$ 20,340