Related Parties (Narrative) (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2015 property	Mar. 31, 2014	Dec. 31, 2014 property	Dec. 31, 2013 property
Related Party Transaction [Line Items]
Net accounts receivable, related parties	$ 1,300,000		$ 1,500,000
Accounts payable and accrued expenses, related parties	5,500,000		6,000,000
Management fees revenues, related parties	1,200,000	1,200,000
Total assets	3,837,009,000		3,814,094,000
Debt, net	1,738,686,000
Increase in equity	0	10,932,000
Number of operating properties sold	3
Gain on sale of property	22,522,000	41,375,000
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			11,000,000
Number of operating properties sold			8
Gain on sale of property			$ 23,300,000