Business Acquisitions (Details Textual) (USD $) Share data in Millions, unless otherwise specified	9 Months Ended			1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended						1 Months Ended	9 Months Ended			9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Mar. 31, 2013	Oct. 31, 2013 Subsequent Event [Member]	Sep. 30, 2013 Cb Portfolio Acquisition [Member]	Sep. 30, 2013 Cb Portfolio Acquisition [Member]	Dec. 31, 2012 Cb Portfolio Acquisition [Member]	Feb. 28, 2013 Cb Portfolio Acquisition [Member]	Sep. 30, 2013 Cb Portfolio Acquisition [Member] Cb Investors [Member]	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]	Sep. 30, 2013 Copper Beech [Member]	Feb. 28, 2013 Copper Beech [Member]	Jul. 31, 2013 Montreal Quebec Acquisition [Member]	Sep. 30, 2013 DCV Holdings, LP [Member]	Sep. 30, 2013 Copper Beech Purchase Agreement [Member]	Sep. 30, 2013 March 18, 2014 to August 18, 2014 [Member]	Sep. 30, 2013 May 2015 [Member]	Sep. 30, 2013 May 2016 [Member]	Mar. 31, 2013 Campus Crest At Toledo Ohio [Member]
Business Acquisitions Costs Of Acquired Entity Purchase Price			$ 13,801,000												$ 230,200,000	$ 0						$ 13,800,000
Company Ownership Percentage								48.00%		52.00%	36.30%	11.70%	48.00%				20.00%	48.00%				100.00%
Student Housing Properties Average Age In Year						7 years 2 months 12 days
Payments to Acquire Businesses, Gross						13,000,000
Due from Other Related Parties									31,700,000
Income (Loss) from Equity Method Investments	3,608,000	(135,000)			1,500,000	3,600,000
Investment Income, Interest					700,000	1,400,000
Business Combination, Acquisition Related Costs						700,000								16,800,000
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares						25.5
Average Monthly Total Revenue Per Occupied Bed							470
Mortgage Loans on Real Estate, Interest Rate						8.50%
Mortgage Loans On Real Estate Interest Rate Of Tem Period						3 years
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	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, we will hold a 67.0% interest in each of 30 properties in the Copper Beech Portfolio, with the CB Investors holding the remaining 33.0% interest. In addition, under the terms of the Amendment, we have the option, exercisable from March 18, 2014 through August 18, 2014, to acquire an 18.0% interest in each of the seven properties whose acquisition is being deferred (collectively, the “Deferred Copper Beech Properties”), which will entitle us to 33.0% of the operating cash flows of such Deferred Copper Beech Properties
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%
Description for acquire additional interests in Portfolio Acquisition																			Beginning March 18, 2014 through August 18, 2014, we have the option to acquire an additional 18.0% interest in the Initial Copper Beech Properties, increasing our aggregate interest in such properties to 85.0%, which will entitle us to 100% of the operating cash flows of the Initial Copper Beech Properties.	Through May 2015, we have the option to acquire an additional 3.9% interest in the Initial Copper Beech Properties and an additional 70.9% interest in the Deferred Copper Beech Properties, increasing our aggregate interest in all 37 properties in the Copper Beech Portfolio to 88.9%, which will entitle us to 100% of the operating cash flows of the Initial Copper Beech Properties and the Deferred Copper Beech Properties.	Through May 2016, we have the option to acquire an additional 11.1% interest in the Copper Beech Portfolio, increasing our aggregate interest to 100%.
Repayment of outstanding principal balance				31,700,000
Payments to Acquire Interest in Joint Venture																	$ 60,000,000
Business Acquisition Purchase Option One	If the first purchase option is not exercised, we will be entitled to a 48.0% interest in all 37 properties in the CB Portfolio and will be entitled to 48.0% of operating cash flows and 45.0% of the proceeds of any sale of any portion of the CB Portfolio.
Business Acquisition Purchase Option Two	If the first purchase option is exercised but the second purchase option is not exercised, we will be entitled to a 75.0% interest in all 37 properties in the CB Portfolio and will be entitled to 75.0% of operating cash flows and 70.0% of the proceeds of any sale of any portion of the CB Portfolio.
Business Acquisition Purchase Option Three	If the second purchase option is exercised but the third purchase option is not exercised, we will retain our 88.9% interest in the CB Portfolio and will be entitled to 88.9% of both operating cash flows and the proceeds of any sale of any portion of the CB Portfolio.