Business (Narratives) (Details)	6 Months Ended
	Jun. 30, 2013 tenant property sqft
Additional disclosures
Square footage of all real estate properties	39,500,000
Number of real estate properties	423
Number of tenants	123
Occupancy rate	98.90%
Managed Reits
Additional disclosures
Square footage of all real estate properties	77,300,000
Number of real estate properties	700
Number of tenants	216
Occupancy rate	98.80%