EARNINGS PER COMMON SHARE (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reconciliation of basic and diluted net income and distributions per common share
Net income	$ 68,876	$ 39,886	$ 86,132	$ 98,336	$ 77,013	$ 111,964	$ 71,205	$ 88,048	$ 293,230	$ 348,230	$ 318,072
Less: Preferred share distributions	6,891	6,891	6,891	6,738					27,411
Net income available to common shareholders	61,985	32,995	79,241	91,598					265,819	348,230	318,072
Less: Dividends and undistributed earnings allocated to participating securities									904	1,116	1,082
Net income allocated to common shareholders									264,915	347,114	316,990
Effect of dilutive securities:
Interest on convertible senior notes										3,234
Net income allocated to common shareholders for diluted earnings per share									264,915	350,348	316,990
Basic:
Basic weighted average common shares outstanding (in shares)	204,154,000	204,134,000	204,108,000	197,153,000	177,906,000	177,862,000	177,809,000	177,775,000	202,411,000	177,838,000	177,560,000
Net income per common share (in dollars per share)	$ 0.30	$ 0.16	$ 0.39	$ 0.46	$ 0.43	$ 0.63	$ 0.40	$ 0.49	$ 1.31	$ 1.95	$ 1.79
Diluted:
Basic weighted average common shares outstanding (in shares)	204,154,000	204,134,000	204,108,000	197,153,000	177,906,000	177,862,000	177,809,000	177,775,000	202,411,000	177,838,000	177,560,000
Dilutive effect of convertible senior notes (in shares)										9,585,000	3,337,000
Diluted weighted average common shares outstanding (in shares)	204,154,000	204,134,000	204,108,000	197,153,000	202,371,000	183,431,000	181,642,000	182,247,000	202,411,000	187,423,000	180,897,000
Net income per common share (in dollars per share)	$ 0.30	$ 0.16	$ 0.39	$ 0.46	$ 0.40	$ 0.61	$ 0.39	$ 0.48	$ 1.31	$ 1.87	$ 1.75
Amount of debt that had been tendered for conversion				$ 172,500					$ 186,254
Number of common shares of the entity issued in exchange of convertible notes (in shares)				26,100,000
Anti-dilutive securities
Anti-dilutive securities excluded from diluted earnings per share calculations (in shares)									1,932,279	1,932,279	1,932,279