Equity (Details Textual) $ / shares in Units, $ in Millions		3 Months Ended
	Mar. 11, 2016 shares	Mar. 31, 2016 USD ($) shares $ / shares	Dec. 31, 2015 $ / shares shares
Common Stock Disclosures [Abstract]
Common shares of beneficial interest, shares authorized		500,000,000	500,000,000
Common shares of beneficial interest, par value (usd per share) | $ / shares		$ 0.01	$ 0.01
Stock Repurchase Program, Authorized Amount | $		$ 150.0
Preferred Stock Disclosures [Abstract]
Preferred shares of beneficial interest, shares authorized		100,000,000	100,000,000
Preferred shares of beneficial interest, par value (usd per share) | $ / shares		$ 0.01	$ 0.01
Preferred shares of beneficial interest, shares outstanding		8,400,000	14,000,000
Preferred shares of beneficial interest, redemption price per share (usd per share) | $ / shares		$ 25.00
LTIP Units Disclosures [Abstract]
Operating Partnership outstanding		236,351	236,351
LTIP units, vested		54,845
6.50% Series C [Member]
Preferred Stock Disclosures [Abstract]
Preferred shares of beneficial interest, shares outstanding		5,000,000	5,000,000
Preferred Stock, Dividend Rate, Percentage		6.50%	6.50%
Share cap on each preferred shares		2.0325
7.875% Series A [Member]
Preferred Stock Disclosures [Abstract]
Stock Redeemed or Called During Period, Shares	5,600,000
Preferred shares of beneficial interest, shares outstanding		0	5,600,000
Preferred Stock, Dividend Rate, Percentage	7.875%		7.875%
8.00% Series B [Member]
Preferred Stock Disclosures [Abstract]
Preferred shares of beneficial interest, shares outstanding		3,400,000	3,400,000
Preferred Stock, Dividend Rate, Percentage		8.00%	8.00%
Share cap on each preferred shares		3.4483
ATMProgram [Member]
Common Stock Disclosures [Abstract]
Mar 2014 Shelf Registration Stmt Maximum Amount | $		$ 175.0
Sept 2012 Shelf Registration Stmt Maximum Amount | $		170.0
Amount Available under ATM Program | $		$ 159.8