Related Party Transactions - Additional Information (Detail) (USD $)	1 Months Ended	9 Months Ended							9 Months Ended	12 Months Ended														3 Months Ended	9 Months Ended	12 Months Ended		1 Months Ended	9 Months Ended			1 Months Ended	9 Months Ended
	Feb. 28, 2013	Sep. 30, 2013 Property	Dec. 31, 2012 Property	Sep. 30, 2013 Class A Common Shares [Member]	Dec. 31, 2012 Class A Common Shares [Member]	Sep. 30, 2013 Class B Common Shares [Member]	Dec. 31, 2012 Class B Common Shares [Member]	Feb. 28, 2013 2,770 Property Contribution [Member] Property	Sep. 30, 2013 Sponsor [Member]	Dec. 31, 2012 Sponsor [Member]	Sep. 30, 2013 Sponsor [Member] Class A Common Shares [Member]	Dec. 31, 2012 Sponsor [Member] Class A Common Shares [Member]	Sep. 30, 2013 Sponsor [Member] Class B Common Shares [Member]	Dec. 31, 2012 Sponsor [Member] Class B Common Shares [Member]	Sep. 30, 2013 Sponsor [Member] Class A Units [Member]	Dec. 31, 2012 Sponsor [Member] Class A Units [Member]	Dec. 31, 2012 Sponsor [Member] 3.5% Convertible Perpetual Preferred Units [Member]	Sep. 30, 2013 Sponsor [Member] Series C Convertible Units [Member]	Sep. 30, 2013 Sponsor [Member] Series D Convertible Units [Member]	Sep. 30, 2013 Sponsor [Member] Series E Convertible Units [Member]	Sep. 30, 2013 Sponsor [Member] 2,770 Property Contribution [Member] Property	Dec. 31, 2012 Sponsor [Member] 2,770 Property Contribution [Member] Property	Dec. 31, 2011 Sponsor [Member] 2,770 Property Contribution [Member] Property	Sep. 30, 2013 Sponsor [Member] Agreement on Investment Opportunities [Member]	Sep. 30, 2013 Sponsor [Member] Agreement on Investment Opportunities [Member]	Dec. 31, 2012 Sponsor [Member] Agreement on Investment Opportunities [Member]	Nov. 30, 2012 Sponsor [Member] Agreement on Investment Opportunities [Member]	Nov. 30, 2012 Advisor [Member]	Sep. 30, 2013 Advisor [Member]	Dec. 31, 2012 Advisor [Member]	Feb. 28, 2013 Advisor [Member] 2,770 Property Contribution [Member] Property	Nov. 30, 2012 Property Manager [Member]	Sep. 30, 2013 Property Manager [Member] Deferred Costs and Other Intangibles [Member]	Sep. 30, 2013 Property Manager [Member] Operating Expenses [Member]
Related Party Transaction [Line Items]
Common shares owned											3.70%	8.50%
Common shares outstanding				184,856,219	38,663,998	635,075	667						635,075	667
Units outstanding															13,787,292	32,668		31,085,974	4,375,000	4,375,000
Preferred units outstanding																	653,492
Equity interest rate									25.60%	17.20%
Advisory management fee in percent																												1.75%
Permanent reduction in Advisory management fee	$ 9,800,000																											$ 9,800,000
Number of properties		21,267	3,644					2,770													109	2,628	33								2,770
Advisory fees		6,352,000																											6,352,000
Accrued management fees																														937,000
Property management fee in percent																																6.00%
Leasing fee description																																One-half month of each lease's annual rent
Fees incurred to the Property Manager																																	2,888,000	1,264,000
Acquisition and renovation fee in percent																											5.00%
Monthly maintenance fee																									100,000
Acquisition and renovation fees																								22,947,000	95,319,000
Asset acquisition cost																								22,666,000	92,718,000
Property acquisition cost																								281,000	2,601,000
Accrued acquisition and renovation fees																									$ 1,120,000	$ 2,811,000