Related Party Arrangements (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Apr. 01, 2015
Related party arrangements
Related Party Transaction, Amounts of Transaction	$ 7,876,000	$ 8,138,000
Expensed	7,316,000	7,643,000
Related Party Transaction, Costs Capitalized to Real Estate Under Development	0	207,000
Capitalized to building and improvements, net	560,000	288,000
Amount payable to related parties	2,257,000		2,041,000
BHT Advisors
Related party arrangements
Contract termination fee				2,700,000
Gross service charge payable multiplier to determine termination payment	0.75
Period over which services payable would be calculated	12 months
BHT Advisors, acquisition fees	100,000	207,000
BHT Advisors, cost of services provided	650,000	640,000
HPT Management
Related party arrangements
Gross Management and Oversight Fees Earned Multiplier to Derive Buyout Consideration	0.8
Period over which services payable would be calculated	12 months
HPT Management, property and construction management fees	2,870,000	2,794,000
HPT Management, reimbursement of costs and expenses	$ 4,256,000	$ 4,497,000