SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash Flow Statements [Abstract]
Paid interest	$ 74,300,000	$ 108,600,000	$ 146,900,000
Income taxes paid	28,100,000	11,600,000	1,900,000
Securities [Abstract]
Amortized cost of held-to-maturity securities reclassified to available-for-sale		1,600,000,000
Fair value of held-to-maturity securities reclassified to available-for-sale		1,700,000,000
Increase in other comprehensive income due to transfers to available-for-sale securities		19,700,000
Loans and Leases [Abstract]
Threshold loan amount for which an appraisal is obtained for real estate collateral	250,000
Threshold loan amount for which a new appraisal is ordered, when characteristics of potential impairment exist	200,000
Period over which an appraisal is considered current	12 months
Impaired loans	156,728,000	234,923,000
Cumulative charge-offs during the period	49,300,000
Specific reserves included in the allowance for credit losses	10,500,000
Marketing period	180 days
Days past due of principal or interest at which loans and leases may be placed in non-accrual status	90 days	90 days
Minimum sustained period of repayment performance for TDR loans to return to accrual status	6 months
Loans held for sale [Abstract]
Number of mortgage loans repurchased	14	7
Amount of mortgage loans repurchased	2,100,000	803,000
Losses recognized related to repurchased and make whole loans	782,000	181,000
Amount reserved for potential losses from representation and warranty obligations	729,000
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	21,800,000
Stock-Based Compensation [Abstract]
Number of stock-based employee compensation plans	3
Compensation costs for unvested awards granted	1,900,000	2,100,000	2,100,000
Derivative Instruments [Abstract]
Notional amount	$ 496,200,000	$ 493,300,000
Average maturity	59 months 27 days	62 months 9 days
Average interest receive rate (in hundredths)	2.50%	2.60%
Average interest pay rate (in hundredths)	5.70%	5.90%
Basic Plan [Member]
Pension and Postretirement Benefits Accounting [Abstract]
Discount rate assumptions for determination of projected benefit obligation (in hundredths)	4.05%	4.80%
Restoration Plan [Member]
Pension and Postretirement Benefits Accounting [Abstract]
Discount rate assumptions for determination of projected benefit obligation (in hundredths)	3.65%	4.45%
Supplemental Plan [Member]
Pension and Postretirement Benefits Accounting [Abstract]
Discount rate assumptions for determination of projected benefit obligation (in hundredths)	2.85%	3.85%