MORTGAGE SERVICING RIGHTS (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Data and assumptions used in fair value calculation [Abstract]
Unpaid principal balance	$ 4,841,075,000	$ 4,143,880,000	$ 4,841,075,000	$ 4,143,880,000	$ 4,293,552,000
Weighted-average prepayment speed (CPR) (in hundredths)			18.40%	22.70%	22.70%
Discount rate (annual percentage) (in hundredths)			10.80%	10.30%	10.30%
Weighted-average coupon interest rate (percentage) (in hundredths)			4.50%	5.10%	4.90%
Weighted-average remaining maturity (in months)			307 months	314 months	311 months
Weighted-average servicing fee basis points (in hundredths)			27.40%	28.10%	28.00%
Activity in mortgage servicing asset [Roll Forward]
Fair value as of beginning of period			30,174,000	38,642,000	38,642,000
Additions:
Origination of servicing assets			13,385,000	7,938,000
Changes in fair value:
Due to payoffs/paydowns			(5,644,000)	(4,435,000)
Due to change in valuation inputs or assumptions used in the valuation model			(3,346,000)	(12,975,000)
Other changes in fair value			(7,000)	(11,000)
Fair value as of end of period	34,562,000	29,159,000	34,562,000	29,159,000	30,174,000
Contractually specified servicing fees, late fees, and ancillary fees [Abstract]
Contractual servicing fees	3,200,000	2,900,000	9,500,000	8,600,000
Late and other ancillary fees	$ 361,000	$ 334,000	$ 1,000,000	$ 966,000