SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2011	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Cash Flow Statements [Abstract]
Paid interest		$ 108,600,000	$ 146,900,000	$ 171,700,000
Income taxes paid		11,600,000	1,900,000	8,700,000
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 (in months)		12M
Impaired loans		234,923,000	273,405,000
Cumulative charge-offs during the period		52,200,000
Specific reserves included in the allowance for credit losses		39,700,000
Marketing period (in days)		180D
Days past due of principal or interest at which loans and leases may be placed in non-accrual status (in days)	90D	90D
Minimum sustained period of repayment performance for TDR loans to return to accrual status (in months)		6M
Loans held for sale [Abstract]
Number of mortgage loans repurchased		7	11
Amount of mortgage loans repurchased		803,000	1,600,000
Losses recognized related to repurchased and make whole loans		181,000	314,000
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		21,500,000
Stock-Based Compensation [Abstract]
Number of stock-based employee compensation plans			3
Compensation costs for unvested awards granted		2,100,000	2,200,000	1,700,000
Derivative Instruments [Abstract]
Notional amount		$ 493,300,000	$ 514,800,000
Average maturity (in months)		62.3M	73.4M
Average interest receive rate (in hundredths)		2.60%	2.50%
Average interest pay rate (in hundredths)		5.90%	6.10%
Basic Plan [Member]
Pension and Postretirement Benefits Accounting [Abstract]
Discount rate assumptions for determination of projected benefit obligation (in hundredths)		4.80%	5.50%
Restoration Plan [Member]
Pension and Postretirement Benefits Accounting [Abstract]
Discount rate assumptions for determination of projected benefit obligation (in hundredths)		4.45%	5.15%
Supplemental Plan [Member]
Pension and Postretirement Benefits Accounting [Abstract]
Discount rate assumptions for determination of projected benefit obligation (in hundredths)		3.85%	4.50%