STOCKHOLDERS' EQUITY AND EARNINGS PER SHARE (Details 5) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012		Dec. 31, 2011	Dec. 31, 2010
Earnings per share calculations
Net income									$ 281,065		$ 245,234	$ 164,564
Less: Preferred stock dividends	(1,715)	(1,714)	(1,714)	(1,714)	(1,714)	(1,714)	(1,714)	(1,715)	(6,857)		(6,857)	(43,126)
Less: Earnings allocated to participating securities									(3,271)
Basic EPS - income allocated to common stockholders									270,937	[1]	238,377	121,438
Effect of dilutive securities
Restricted stock awards									47		115	15
Convertible preferred stock									6,857		6,857
Diluted EPS - income allocated to common stockholders									$ 277,841	[1]	$ 245,349	$ 121,453
Number of Shares
Weighted average shares outstanding									141,457		147,093	137,478
Effect of dilutive securities on weighted average shares outstanding
Stock options (in shares)									29		62	142
Restricted stock awards (in shares)									118		718	370
Convertible preferred stock (in shares)									5,571		5,571	8,936
Stock warrants (in shares)											23	176
Total weighted average diluted shares outstanding									147,175		153,467	147,102
Per Share Amounts
Basic EPS (in dollars per share)	$ 0.50	$ 0.49	$ 0.48	$ 0.46	$ 0.44	$ 0.41	$ 0.40	$ 0.37	$ 1.92		$ 1.62	$ 0.88
Diluted EPS - Income available to common stockholders (in dollars per share)	$ 0.49	$ 0.48	$ 0.47	$ 0.45	$ 0.43	$ 0.41	$ 0.39	$ 0.37	$ 1.89		$ 1.60	$ 0.83

[1] On April 1, 2012, the Company revised its calculation of earnings per share to account for participating securities under the two-class method. This revision to the earnings per share calculation does not have an impact to previous periods as the amounts are immaterial.