Real Estate Investments (Assets and Liabilities Assumed) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended			39 Months Ended
	Dec. 31, 2012 property	Dec. 31, 2011 property	Dec. 31, 2010 property	Dec. 31, 2012 property
Real estate investments, at cost:
Land	$ 74,209	$ 7,196	$ 11,243
Buildings, fixtures and improvements	131,958	46,085	50,051
Total tangible assets	206,167	53,281	61,294
Acquired intangibles	22,911	4,645	4,956
Total assets acquired, net	229,078	57,926	66,250
Mortgage notes payable used to acquire investments in real estate	(79,188)	(32,650)	(35,521)
Non-controlling Interest Retained by Seller	(380)	0	0
Other liabilities assumed	(4,760)	0	0
Cash paid for acquired real estate investments	144,750	25,276	30,729
Number of properties purchased	7	5	4	16
Leases, Acquired-in-Place [Member]
Real estate investments, at cost:
Acquired intangibles	18,867	5,194	6,215
Above Market Leases [Member]
Real estate investments, at cost:
Acquired intangibles	9,194	0	106
Below Market Leases [Member]
Real estate investments, at cost:
Acquired intangibles	$ (5,150)	$ (549)	$ (1,365)