Interim Financial Statements (Operating Partnership) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
The Operating Partnership [Abstract]
Number Of Classes Of Preferred Stock	three
Common stock, shares outstanding	60,685,420		60,430,613
Number Of Classes Of Preferred Equity	two
Noncontrolling Interest, Ownership Percentage by Parent	71.00%
Limited Liability Company (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest	71.00%	71.00%
Units of Partnership Interest, Amount	85,656,699
Number Of Operating Partnership Units Outstanding Owned By Company	60,685,420
Restructuring Charges	$ 1,896
Costs Associated With Shareowner Activism	$ 3,500
Substantial Doubt about Going Concern, Management's Evaluation	When preparing financial statements for each annual and interim reporting period, management has the responsibility to evaluate whether there are conditions or events, considered in the aggregate, that raise substantial doubt about the Company's ability to continue as a going concern within one year after the date that the financial statements are issued. No such conditions or events were identified as of the issuance date of the financial statements contained in this Quarterly Report on Form 10-Q.
Series J Preferred Stock [Member]
The Operating Partnership [Abstract]
Dividend rate (in hundredths)	6.50%
Preferred Stock, Shares Outstanding	7,700,000		7,700,000
Series K Preferred Stock [Member]
The Operating Partnership [Abstract]
Dividend rate (in hundredths)	6.25%
Preferred Stock, Shares Outstanding	6,800,000		6,800,000
Series B Preferred Stock [Member]
The Operating Partnership [Abstract]
Units of Partnership Interest, Terms of Conversion	one share of nonparticipating Series B Preferred Stock per each Operating Partnership unit
Preferred Stock, voting rights	one vote per share
Convertible Preferred Stock, Terms of Conversion	ratio of 14,000 shares of Series B Preferred Stock for one share of common stock
Preferred Stock, Shares Outstanding	24,954,059		25,029,059