SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS Common Shares (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Common Stock [Member]
Class of Stock [Line Items]
Issuance of Common Shares, net of issuance costs (in Shares)	12,237,000	3,013,000	9,510,000
Conversion of OP Units to Common Shares by limited partners of the Operating Partnership (in Shares)	136,000	93,000	334,000
ATM Equity Program [Member]
Class of Stock [Line Items]
Proceeds from issuance of common stock	127.1		140.8
ATM Equity Program [Member] | Common Stock [Member]
Class of Stock [Line Items]
Issuance of Common Shares, net of issuance costs (in Shares)	4,400,000	3,000,000	6,100,000
Proceeds from issuance of common stock		80.7
Public Offering [Member]
Class of Stock [Line Items]
Proceeds from issuance of common stock	230.7		85.9
Public Offering [Member] | Common Stock [Member]
Class of Stock [Line Items]
Issuance of Common Shares, net of issuance costs (in Shares)	7,600,000		3,500,000
Common Op Units Conversion To Common Shares [Member] | Common Stock [Member]
Class of Stock [Line Items]
Conversion of OP Units to Common Shares by limited partners of the Operating Partnership (in Shares)	1,600,000	1,200,000	250,000
Restricted Stock [Member]
Class of Stock [Line Items]
Restricted stock, shares canceled for tax withholding for share based compensation	3,886
LTIP Units and Restricted Stock [Member]
Class of Stock [Line Items]
Unit based compensation	6.2	0.5