Commitments and Contingencies - Additional Information (Detail) (USD $)	9 Months Ended			12 Months Ended		12 Months Ended			12 Months Ended	6 Months Ended	12 Months Ended
	Sep. 30, 2012	Oct. 30, 2012	Aug. 06, 2012	Dec. 31, 2010 Colony Park	Dec. 31, 2010 Colony Park Maximum	Dec. 31, 2011 Membership Class Action	Dec. 31, 2010 Hurricane Claim Litigation	Jun. 22, 2007 Hurricane Claim Litigation	Dec. 31, 2010 Attorney Fees Colony Park	Jun. 30, 2009 Attorney Fees California Rent Control Litigation Final Resolution in Favor of Company	Dec. 31, 2008 Cascade [Member]	Dec. 30, 2008 Cascade [Member]	Oct. 09, 2012 Subsequent Event [Member] Utah Utility Class Action [Member]
Loss Contingencies [Line Items]
Award for costs and attorney fee claimed									$ 2,000,000	$ 2,100,000	$ 7,050,000
Expiration period of Ordinance from June 30, 2009 date of judgment										10 years
Loss award claimed by plaintiffs				6,800,000									1,000,000
Loss awarded to plaintiffs					44,000
Number of plaintiff				72		2
Negotiated Property Sale Price											12,500,000
Number of plaintiff the jury rendered verdicts				6
Number of plaintiffs dismissed				66
Loss Contingency Claims Dismissed And Not Appealed Number				3
Claims filed against Aon								11,000,000
Proceeds from insurance	14,700,000						7,400,000
Loss Contingency, Estimate of Possible Loss		500,000	2,400,000
Earnest Money Deposits												400,000
Compensatory Rate Increase												5.00%
Promissory Note Percentage												50.00%
Gain Contingency, Unrecorded Amount												12,150,000
Promisorry Note											$ 30,000,000