Related Party Transactions - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012		Dec. 31, 2011
Related Party Transaction [Line Items]
Percentage of outstanding Wraparound mortgages payable owned by NPAEP	100.00%
Due to related party	$ 3,412	[1]	$ 3,379	[1]
Maximum borrowing capacity	2,500
Variable rate of interest on prime rate	3.25%
Line of credit facility, expiration date	December 2013
Line of credit facility, amount outstanding	610
Accrued interest	146
Annual rental payments to NPAEP	32
Proceeds from Lines of Credit	416
Accounts Payable And Other Liabilities
Related Party Transaction [Line Items]
Due to related party	$ 2,794		$ 2,729

[1] See Note 3: Related Party Transactions.