Mortgage Banking (Details) (USD $)	3 Months Ended		6 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Jun. 30, 2012	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Mortgage Banking [Abstract]
Gain (Loss) on Fair Value Hedge Ineffectiveness, Net	$ (1,800,000)	$ 2,800,000		$ (2,700,000)	$ 4,800,000
Mortgage servicing rights [Abstract]
Balance at beginning of period			43,274,000	43,274,000	51,151,000	51,151,000
Origination of servicing assets				17,074,000	9,581,000
Change in fair value:
Due to market changes				(8,960,000)	(12,288,000)
Due to runoff				(7,177,000)	(4,785,000)
Balance at end of period	44,211,000	43,659,000		44,211,000	43,659,000	43,274,000
Mortgage loan servicing representation and warranty expenses incurred				7,200,000	2,500,000
Accrual for mortgage loan servicing representation and warranty expenses			$ 4,000,000	$ 8,600,000		$ 4,300,000