MORTGAGE SERVICING RIGHTS (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Data and assumptions used in fair value calculation [Abstract]
Unpaid principal balance	$ 5,058,912,000	$ 4,293,552,000	$ 3,870,872,000
Weighted-average prepayment speed (CPR) (in hundredths)	17.10%	22.70%	15.60%
Discount rate (annual percentage) (in hundredths)	10.80%	10.30%	10.30%
Weighted-average coupon interest rate (percentage) (in hundredths)	4.40%	4.90%	5.20%
Weighted-average remaining maturity (months)	307 months	311 months	315 months
Weighted-average servicing fee basis points (in hundredths)	27.10%	28.00%	28.40%
Contractually specified servicing fees, late fees, and ancillary fees [Abstract]
Contractual servicing fees	13,000,000	11,600,000	10,500,000
Late and other ancillary fees	1,400,000	1,300,000	1,400,000
Closed End Loans for One-to-Four Family Residences, Secured by First Liens [Member]
Activity in mortgage servicing asset [Roll Forward]
Fair value as of beginning of period	30,174,000	38,642,000
Additions [Abstract]
Origination of servicing assets	18,531,000	11,692,000
Changes in fair value [Abstract]
Due to payoffs/paydowns	(7,649,000)	(6,180,000)
Due to change in valuation inputs or assumptions used in the valuation model	(3,163,000)	(13,966,000)
Other changes in fair value	(11,000)	(14,000)
Fair value as of end of period	$ 37,882,000	$ 30,174,000