Related Parties (Narrative) (Details) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) property	Jun. 30, 2014 USD ($)	Dec. 31, 2014 USD ($) property	Dec. 31, 2013 USD ($) property
Related Party Transaction [Line Items]
Net accounts receivable, related parties	$ 1,600		$ 1,600		$ 1,500
Accounts payable and accrued expenses, related parties	5,500		5,500		6,000
Management fees revenues, related parties	1,100	$ 1,100	2,300	$ 2,400
Total assets	3,850,778		3,850,778		$ 3,814,094
Debt, net	$ 1,919,193		$ 1,919,193
Number of operating properties sold | property			6
Gain on sale of property			$ 30,685	46,493
Disposition of noncontrolling interests				(144,263)
Acquisition of noncontrolling interests				0
Hines [Member]
Related Party Transaction [Line Items]
Ownership percentage in joint ventures					30.00%
Number of real estate properties | property					5	13
Total assets						$ 172,900
Debt, net						$ 11,100
Number of operating properties sold | property					8
Gain on sale of property					$ 23,300
Disposition of noncontrolling interests					144,300
Noncontrolling Interests [Member]
Related Party Transaction [Line Items]
Disposition of noncontrolling interests				(144,263)
Acquisition of noncontrolling interests				11,015
Noncontrolling Interests [Member] | Hines [Member]
Related Party Transaction [Line Items]
Acquisition of noncontrolling interests					11,000
Additional Paid-In Capital [Member]
Related Party Transaction [Line Items]
Acquisition of noncontrolling interests				$ (11,015)
Additional Paid-In Capital [Member] | Hines [Member]
Related Party Transaction [Line Items]
Acquisition of noncontrolling interests					$ (11,000)