STOCKHOLDERS' EQUITY (Details) (USD $)	3 Months Ended	12 Months Ended			1 Months Ended	2 Months Ended
	Jan. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	May 31, 2013	Feb. 27, 2015
Stockholders' Equity [Line Items]
Redemption preference premiums paid		$ 0	$ 19,924,000	$ 0
Proceeds from issuance of common stock		0	0	142,035,000
Preferred equity shares capital		18,180,000	165,756,000	4,479,000
Common stock repurchase program	100,000,000
Shares repurchased (in shares)	3,600,000
Value of stock repurchased	42,400,000
Cumulative Redeemable Preferred Stock, Series E [Member]
Stockholders' Equity [Line Items]
Redeemable preferred stock, shares issued (in shares)					6,800,000
Redeemable preferred stock, face value					170,000,000
Preferred stock dividend rate (in hundredths)					7.50%
Redeemable preferred stock, liquidation preference per share (in dollars per share)					$ 25.00
Cash on hand used in capital transactions					42,700,000
Net proceeds					164,300,000
Convertible Preferred Stock [Member]
Stockholders' Equity [Line Items]
Cash used for redemption of preferred stock			207,000,000
Redemption preference premiums paid			19,900,000
Reduction in income per share (in dollars per share)			$ 0.21
Shares (in shares)				309,000
Additional shares issued (in shares)				309,000
Preferred equity shares capital				4,500,000
Continuous Offering Program [Member]
Stockholders' Equity [Line Items]
Shares (in shares)				10,500,000
Proceeds from issuance of common stock				142,000,000
Additional shares issued (in shares)				10,500,000
Continuous Offering Program [Member] | Cumulative Redeemable Preferred Stock, Series E [Member]
Stockholders' Equity [Line Items]
Shares (in shares)		757,000	61,000
Net Issue Price (In dollars per share)		$ 24.01	$ 23.78
Net proceeds		18,180,000	1,447,000
Additional shares issued (in shares)		757,000	61,000
Continuous Offering Program [Member] | Cumulative Redeemable Preferred Stock, Series E [Member] | Subsequent Event [Member]
Stockholders' Equity [Line Items]
Shares (in shares)						222,000
Net Issue Price (In dollars per share)						$ 24.65
Net proceeds						5,465,000
Additional shares issued (in shares)						222,000
Directors And Employees [Member]
Stockholders' Equity [Line Items]
Additions to common equity capital related to equity-based awards		$ 1,900,000	$ 1,800,000	$ 4,400,000