Related Parties (Narrative) (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2014 property	Mar. 31, 2013	Dec. 31, 2013 property
Related Party Transaction [Line Items]
Net accounts receivable, related parties	$ 1,100,000		$ 1,400,000
Accounts payable and accrued expenses, related parties	5,400,000		5,600,000
Management fees revenues, related parties	1,200,000	1,400,000
Ownership percentage in joint ventures			50.00%
Total assets	3,869,172,000		4,223,929,000
Debt, net	1,834,968,000
Increase in equity	10,932,000	0
Number of operating properties sold	11		20
Number of properties held for sale	1		8
Gain on sale of property	41,375,000	142,000
Hines [Member]
Related Party Transaction [Line Items]
Ownership percentage in joint ventures	30.00%
Number of real estate properties	5		13
Total assets			172,900,000
Debt, net			11,100,000
Increase in equity	10,900,000
Number of operating properties sold	8
Gain on sale of property	23,100,000
Tenancy In Common [Member]
Related Party Transaction [Line Items]
Ownership percentage in joint ventures			10.00%
Number of real estate joint ventures			2
Gross proceeds, related parties			8,900,000
Consoldiated Real Estate Joint Ventures [Member]
Related Party Transaction [Line Items]
Number of real estate joint ventures			2
Unconsolidated Real Estate Joint Ventures [Member]
Related Party Transaction [Line Items]
Ownership percentage in joint ventures			51.00%
Total assets	$ 1,273,580,000		$ 1,283,166,000
Number of operating properties sold			5
Number of real estate joint ventures			2