EARNINGS PER COMMON SHARE (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Reconciliation of basic and diluted net income and distributions per common share
Net income	$ 98,336,000	$ 88,048,000
Less: Preferred share distributions	6,738,000
Net income available to common shareholders	91,598,000	88,048,000
Less: Dividends and undistributed earnings allocated to participating securities	338,000	297,000
Net income allocated to common shareholders	91,260,000	87,751,000
Basic:
Basic weighted average common shares outstanding (in shares)	197,153,000	177,775,000
Net income per common share (in dollars per share)	$ 0.46	$ 0.49
Diluted:
Basic weighted average common shares outstanding (in shares)	197,153,000	177,775,000
Dilutive effect of convertible senior notes (in shares)		4,472,000
Diluted weighted average common shares outstanding (in shares)	197,153,000	182,247,000
Net income per common share (in dollars per share)	$ 0.46	$ 0.48
Dividends
Distributions declared per common share (in dollars per share)	$ 0.26	$ 0.26
Amount of debt that had been tendered for conversion	$ 172,500,000
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