MORTGAGE SERVICING RIGHTS (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Data and assumptions used in fair value calculation [Abstract]
Unpaid principal balance	$ 5,802,407	$ 5,630,192	$ 5,802,407	$ 5,630,192	$ 5,686,756
Weighted-average prepayment speed (CPR)	10.00%	11.30%			11.60%
Discount rate (annual percentage) (in hundredths)	9.80%	10.30%			9.80%
Weighted-average coupon interest rate (percentage) (in hundredths)	4.10%	4.10%			4.10%
Weighted-average remaining maturity (months)	316 months	312 months			314 months
Weighted-average servicing fee (basis points)	0.266%	0.266%			0.265%
Activity in mortgage servicing asset [Roll Forward]
Fair value as of beginning of period			51,296	54,662	$ 54,662
Additions [Abstract]
Origination of servicing assets			6,843	4,025
Changes in fair value [Abstract]
Due to payoffs/paydowns			(3,494)	(2,754)
Due to change in valuation inputs or assumptions used in the valuation model			1,282	(3,658)
Other changes in fair value			(3)	(3)
Fair value as of end of period	$ 55,924	$ 52,272	55,924	52,272	$ 51,296
Contractually specified servicing fees, late fees, and ancillary fees [Abstract]
Contractual servicing fees	4,000	3,800	7,800	7,500
Late and other ancillary fees	$ 314	$ 306	$ 662	$ 640