Business Acquisitions (Details Textual)	1 Months Ended		3 Months Ended	12 Months Ended												1 Months Ended	12 Months Ended			1 Months Ended			1 Months Ended		12 Months Ended				1 Months Ended
	Jan. 31, 2014 USD ($)	Oct. 31, 2013 USD ($)	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2014 Cb Investors [Member] USD ($)	Dec. 31, 2013 Cb Investors [Member] USD ($)	Dec. 31, 2014 Cb Portfolio Acquisition [Member] USD ($)	Dec. 31, 2013 Cb Portfolio Acquisition [Member] USD ($)	Feb. 28, 2013 Cb Portfolio Acquisition [Member]	Dec. 31, 2014 Cb Portfolio Acquisition [Member] Cb Investors [Member] USD ($)	Feb. 28, 2013 Cb Portfolio Acquisition [Member] Cb Investors [Member]	Feb. 28, 2013 Cb Portfolio Acquisition [Member] Members Of Cbtc and Cbtc Pa [Member]	Feb. 28, 2013 Cb Portfolio Acquisition [Member] Non Member Investors [Member]	Feb. 28, 2013 Cb Portfolio Acquisition [Member] Purchase and Sale Agreement [Member] USD ($)	Dec. 31, 2014 Copper Beech [Member] USD ($)	Dec. 31, 2013 Copper Beech [Member] USD ($)	Feb. 28, 2013 Copper Beech [Member] USD ($)	Jul. 31, 2013 DCV Holdings, LP [Member] CAD	Dec. 31, 2014 CSH Montreal LP [Member]		Sep. 30, 2013 Copper Beech Purchase Agreement [Member] USD ($)	Dec. 31, 2014 Copper Beech Purchase Agreement [Member]	Dec. 31, 2014 March 18, 2014 to August 18, 2014 [Member] USD ($)	Dec. 31, 2014 May 2015 [Member] Subsequent Event [Member] USD ($)	Dec. 31, 2014 May 2016 [Member] Subsequent Event [Member] USD ($)	Jan. 31, 2014 Harrison Street Real Estate [Member]	Jan. 31, 2014 Harrison Street Real Estate Campus Crest [Member] USD ($)	Jan. 31, 2014 Grove At Stateboro Georgia [Member]	Mar. 31, 2013 Campus Crest At Toledo Ohio [Member] USD ($)
Business Acquisitions Costs Of Acquired Entity Purchase Price																			$ 230,200,000												$ 13,800,000
Our Ownership											48.00%		52.00%	36.30%	11.70%	48.00%					47.00%	[1]		48.00%				80.00%	80.00%	20.00%	100.00%
Student Housing Properties Average Age In Year									8 years 2 months 12 days
Payments to Acquire Businesses, Gross	7,700,000			7,700,000					13,000,000
Due from Other Related Parties												31,700,000
Income (Loss) from Equity Method Investments				(5,510,000)	(3,727,000)	361,000											1,600,000	3,800,000
Investment Income, Interest							0	1,400,000
Business Combination, Acquisition Related Costs									3,000,000	1,100,000							4,000,000	16,900,000
Mortgage Loans on Real Estate, Interest Rate									8.50%
Business Combination, Consideration Transferred, Liabilities Incurred																106,700,000									21,000,000	19,000,000
Payment for investors fee																							4,000,000
Business Combination, Contingent Consideration Arrangements, Description				Pursuant to the terms of the Amendment, following receipt of required third party consents, the Company will transfer its 48.0% interest in five properties in the Copper Beech Portfolio (Copper Beech Auburn, Copper Beech Kalamazoo Phase 1, Copper Beech Kalamazoo Phase 2, Copper Beech Oak Hill and Copper Beech Statesboro Phase 1) back to the CB Investors and defer the acquisition of the two Phase II development properties (Cooper Beech Mt. Pleasant Phase 2 and Cooper Beech Statesboro Phase 2) until August 18, 2014 as consideration for an additional 19.0% interest in each of the remaining 30 properties in the Copper Beech Portfolio (the “Initial Copper Beech Properties”). Following the transfer of such properties, the Company held a 67.0% interest in each of 30 properties in the Copper Beech Portfolio, with the CB Investors holding the remaining 33.0% interest.
Business Acquisitions price for exercise of option																	16,900,000								93,500,000	100,700,000	53,400,000
Business Acquisition Percentage for exercise of option interest																	18.00%
Repayment of outstanding principal balance		31,700,000
Payments to Acquire Interest in Joint Venture																				60,000,000
Purchase Price Of Land					32,400,000
Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Loss					300,000
Business Combination, Step Acquisition, Equity Interest in Acquiree, Fair Value																													1,900,000
Business Combination Separately Recognized Transactions Amortization Expense Recognized				1,500,000
Business Combination, Separately Recognized Transactions, Revenues and Gains Recognized				3,900,000
Business Combination, Separately Recognized Transactions, Expenses and Losses Recognized				1,000,000
Business Combination, Separately Recognized Transactions, Net Gains and Losses			$ 33,400,000

[1] As of January 2014, the Company’s ownership increased to 20.0% from 47.0% due to the acquisition of Holiday Inn Midtown in Montreal, Quebec. See discussion above.