SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) (USD $)	3 Months Ended	12 Months Ended
	Jun. 30, 2011	Dec. 31, 2013 loan item	Dec. 31, 2012 loan	Dec. 31, 2011 loan
Cash Flow Statements [Abstract]
Paid interest		$ 51,900,000	$ 74,300,000	$ 108,600,000
Income taxes paid		39,500,000	28,100,000	11,600,000
Unsettled purchases of securities		1,200,000	24,900,000	0
Loans foreclosed and transferred to OREO		29,300,000	32,400,000	125,200,000
Loans and Leases [Abstract]
Threshold loan amount for which a new appraisal is ordered, when characteristics of potential impairment exist		500,000
Threshold loan amount for which an appraisal is obtained for real estate collateral		250,000
Period over which an appraisal is considered current		12 months
Impaired loans		54,943,000	156,728,000
Cumulative charge-offs during the period		42,200,000	89,400,000	142,100,000
Specific reserves included in the allowance for credit losses		4,100,000
Days past due of principal or interest at which loans and leases may be placed in non-accrual status		90 days
Minimum sustained period of repayment performance for TDR loans to return to accrual status		6 months
Securities [Abstract]
Amortized cost of held-to-maturity securities reclassified to available-for-sale	1,600,000,000			1,600,000,000
Fair value of held-to-maturity securities reclassified to available-for-sale	1,700,000,000			1,700,000,000
Increase in other comprehensive income due to transfers to available-for-sale securities	19,700,000
Loans held for sale [Abstract]
Number of mortgage loans repurchased		16	14	7
Amount of mortgage loans repurchased		931,000	2,100,000	803,000
Losses recognized related to repurchased and make whole loans		661,000	782,000	181,000
Amount reserved for potential losses from representation and warranty obligations		1,100,000
Percentage of remaining principal balance of delinquent loans that may be repurchased by the servicer (in hundredths)		100.00%
Amount of loans subject to buy back		20,900,000
Derivative Instruments [Abstract]
Notional amount		412,900,000	496,200,000
Average maturity		54 months 21 days	59 months 27 days
Average interest receive rate (in hundredths)		2.50%	2.50%
Average interest pay rate (in hundredths)		5.60%	5.70%
Stock-Based Compensation [Abstract]
Number of stock-based employee compensation plans		3
Minimum [Member]
Loans and Leases [Abstract]
Marketing period		180 days
Maximum [Member]
Loans and Leases [Abstract]
Marketing period		360 days
Impaired Loans [Member]
Loans and Leases [Abstract]
Cumulative charge-offs during the period		$ 17,200,000
Basic Plan [Member]
Pension and Postretirement Benefits Accounting [Abstract]
Discount rate assumptions for determination of projected benefit obligation (in hundredths)		4.90%	4.05%
Restoration Plan [Member]
Pension and Postretirement Benefits Accounting [Abstract]
Discount rate assumptions for determination of projected benefit obligation (in hundredths)		4.50%	3.65%
Supplemental Plan [Member]
Pension and Postretirement Benefits Accounting [Abstract]
Discount rate assumptions for determination of projected benefit obligation (in hundredths)		3.65%	2.85%