EARNINGS PER SHARE (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
EARNINGS PER SHARE
Authorized common stock (in shares)	199,000,000		199,000,000
Common stock, par value (in dollars per share)	$ 0.01		$ 0.01
Diluted
Income available to common shareholders (in dollars)	$ 40,029	$ 43,809
Shares of common stock	66,155,000	66,196,000
Total average equivalent shares	68,296,000	68,785,000
Net income per share, diluted (in dollars per share)	$ 0.59	$ 0.64
Basic
Income available to common shareholders (in dollars)	$ 40,029	$ 43,809
Shares of common stock	66,155,000	66,196,000
Net income per share, basic (in dollars per share)	$ 0.61	$ 0.66
Stock options
Diluted
Effect of dilutive stock based compensation (in shares)	2,133,000	2,580,000
Restricted stock
Diluted
Effect of dilutive stock based compensation (in shares)	8,000	9,000