EARNINGS PER SHARE - Reconciliation of weighted average shares outstanding (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
EARNINGS PER SHARE
Net income available for stockholders:	$ 53,760	$ 66,040	$ 129,252	$ 219,055
Less: Dividends paid	(21,892)	(17,540)	(65,923)	(52,623)
Undistributed earnings	$ 31,868	$ 48,500	$ 63,329	$ 166,432
Basic shares outstanding:
Common stock	210,899	210,627	211,493	210,664
Restricted shares of common stock	4,169	4,524	4,222	4,547
Basic shares outstanding, Total	215,068	215,151	215,715	215,211
Diluted shares outstanding:
Common stock	210,899	210,627	211,493	210,664
Dilutive effect of stock based awards	1,074	1,494	1,147	1,608
Diluted shares outstanding excluding restricted shares of common stock, Total	211,973	212,121	212,640	212,272
Restricted shares of common stock	4,169	4,524	4,222	4,547
Diluted shares outstanding, Total	216,142	216,645	216,862	216,819