Acquisition, Development, Construction and Disposition Activity (Purchase Price Allocation) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2012 The Park at Crossroads [Member]	Aug. 28, 2012 The Park at Crossroads [Member]	Dec. 31, 2011 The Brixton [Member]	Oct. 17, 2011 The Brixton [Member]
Business Acquisition [Line Items]
Land	$ 28,578		$ 25,638		$ 20,056
Buildings and improvements	225,792		150,028		110,224
Furniture and fixtures	3,313		3,197		2,319
Existing leases and tenant relationships (Other assets)	3,522	[1]	6,313	[1]	4,381	[1]
Acquired debt	28,000	[2],[3],[4]	27,589	[2]	12,892	[2]	24,900	24,900	12,300	12,300
Other liabilities	0		101		0
Total cash paid	$ 233,205		$ 157,688		$ 124,088

[1] See Note 5 for additional information related to intangible assets identified as existing leases and tenant relationships.

[2] Fair value was equal to principal amount of loan assumed in 2013 at the time of acquisition.

[3] Fair value amount of loan assumed in 2011 at the time of acquisition; actual principal amount of loan assumed was $12.3 million.

[4] Fair value amount of loan assumed in 2012 at the time of acquisition; actual principal amount of loan assumed was