Related Parties (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 property	Sep. 30, 2013	Dec. 31, 2013 property
Related Party Transaction [Line Items]
Net accounts receivable, related parties	$ 1,800,000		$ 1,800,000		$ 1,400,000
Accounts payable and accrued expenses, related parties	5,300,000		5,300,000		5,600,000
Management fees revenues, related parties	1,100,000	1,200,000	3,500,000	3,800,000
Ownership percentage in joint ventures					50.00%
Total assets	3,861,224,000		3,861,224,000		4,223,929,000
Debt, net	1,691,592,000		1,691,592,000
Increase in equity			11,015,000	0
Number of operating properties sold			13
Number of properties held for sale			7		8
Gain on sale of property			115,989,000	116,796,000
Gross proceeds, related parties					8,900,000
Hines [Member]
Related Party Transaction [Line Items]
Ownership percentage in joint ventures	30.00%		30.00%
Number of real estate properties	5		5		13
Total assets					172,900,000
Debt, net					11,100,000
Increase in equity			11,000,000
Number of operating properties sold			8
Gain on sale of property			23,300,000
Tenancy In Common [Member]
Related Party Transaction [Line Items]
Ownership percentage in joint ventures					10.00%
Number of real estate joint ventures					2
Consolidated [Member]
Related Party Transaction [Line Items]
Number of real estate joint ventures					2
Unconsolidated [Member]
Related Party Transaction [Line Items]
Ownership percentage in joint ventures	50.00%		50.00%		51.00%
Total assets	$ 1,206,424,000		$ 1,206,424,000		$ 1,283,166,000
Number of operating properties sold			3		5
Number of real estate joint ventures					2