EXCHANGEABLE SENIOR NOTES (Details) (USD $) In Thousands, except Share data, unless otherwise specified				1 Months Ended	6 Months Ended
	Jun. 30, 2012	Dec. 31, 2011	Mar. 31, 2012 Operating Partnership property	Mar. 31, 2007 3.625% Exchangeable Senior Notes due April 1, 2027 Operating Partnership	Jun. 30, 2012 3.625% Exchangeable Senior Notes due April 1, 2027 Operating Partnership	Apr. 26, 2012 3.625% Exchangeable Senior Notes due April 1, 2027 Operating Partnership	Mar. 01, 2012 3.625% Exchangeable Senior Notes due April 1, 2027 Operating Partnership	Mar. 27, 2007 3.625% Exchangeable Senior Notes due April 1, 2027 Operating Partnership
Notes payable
Principal amount of notes issued				$ 250,000
Interest rate (as a percent)					3.625%			3.625%
Conversion ratio, number of shares per $1,000 principal amount, numerator					43.1091
Redemption price as percentage of principal amount of notes plus accrued and unpaid interest					100.00%
Redemption price as percentage of principal amount of notes at request of debt holders and upon occurrence of designated event					100.00%
Principal amount of notes							$ 87,663
Shares of common stock issued	104,136,770	94,783,590				684,685
Exchangeable senior notes exchange price per share (in dollars per share)			23.20