STOCK-BASED COMPENSATION (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013 item
Performance awards
Stock-based compensation
Awards issued	298,500
Estimated fair value of performance shares awarded	$ 9.3
Period over which average return on average equity is calculated	3 years
Minimum percentage of Company's ROE to earn awards under performance awards	10.00%
Number of awards earned when ROE is below 10.0%	0
Minimum percentage of Company's ROE to earn maximum awards under performance awards	11.50%
No. of Awards
Awards granted (in shares)	298,500
SARs
Stock-based compensation
Awards issued	0
Exercisable period of grants from grant date	5 years
Beginning of annual installments from date of grant	1 year
Expiration period from date of grant	10 years
Weighted-Average Base Price per share
Balance at the beginning of the period (in dollars per share)	$ 22.15
SARs exercised / forfeited (in dollars per share)	$ 22.83
Balance at the end of the period (in dollars per share)	$ 22.12
No. of Awards
Balance at the beginning of the period (in shares)	1,641,167
Awards granted (in shares)	0
Awards exercised / forfeited	69,899
Balance at the end of the period (in shares)	1,571,268
SARs | Minimum
Stock-based compensation
Number of annual installments to exercise stock appreciation rights	3
SARs | Maximum
Stock-based compensation
Number of annual installments to exercise stock appreciation rights	4
Restricted stock units
Stock-based compensation
Awards issued	141,000
Estimated fair value of performance shares awarded	$ 4.4
Vesting percentage	50.00%
No. of Awards
Awards granted (in shares)	141,000