MORTGAGE SERVICING RIGHTS (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Data and assumptions used in fair value calculation [Abstract]
Unpaid principal balance	$ 4,293,552,000	$ 3,870,872,000	$ 3,413,202,000
Weighted-average prepayment speed (CPR) (in hundredths)	22.70%	15.60%	15.90%
Discount rate (annual percentage) (in hundredths)	10.30%	10.30%	10.30%
Weighted-average coupon interest rate (percentage) (in hundredths)	4.90%	5.20%	5.60%
Weighted-average remaining maturity (in months)	311.0	315.0	321.0
Weighted-average servicing fee basis points (in hundredths)	0.28%	0.284%	0.288%
Contractually specified servicing fees, late fees, and ancillary fees [Abstract]
Contractual servicing fees	11,600,000	10,500,000	9,500,000
Late and other ancillary fees	1,300,000	1,400,000	1,200,000
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	38,642,000	35,560,000
Additions:
Origination of servicing assets	11,692,000	13,898,000
Changes in fair value:
Due to payoffs/paydowns	(6,180,000)	(6,781,000)
Due to change in valuation inputs or assumptions used in the valuation model	(13,966,000)	(4,029,000)
Other changes in fair value	(14,000)	(6,000)
Fair value as of end of period	$ 30,174,000	$ 38,642,000