Mortgage Servicing Rights (Details) (Mortgage Servicing Rights., USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Mortgage Servicing Rights.
Mortgage Servicing Rights
Residential mortgage loans serviced for third parties	$ 3,100,000,000	$ 3,200,000,000	$ 3,200,000,000
Servicing income, including late and ancillary fees	8,200,000	8,600,000	8,500,000
Change in fair value of the mortgage servicing rights accounted for under the fair value measurement method
Balance at the beginning of the Period	7,131,000	10,226,000	15,332,000
Changes in Fair Value:
Due to Change in Valuation Assumptions	(863,000)	(1,521,000)	(2,546,000)
Due to Payoffs	(1,507,000)	(1,574,000)	(2,560,000)
Total Changes in Fair Value of Mortgage Servicing Rights	(2,370,000)	(3,095,000)	(5,106,000)
Balance at the end of the Period	$ 4,761,000	$ 7,131,000	$ 10,226,000