Operating Leases - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2013 M
Operating Leased Assets [Line Items]
Years, minimum term range of office and retail leases	3 years
Years, maximum term range of office and retail leases	10 years
Months, minimum term of apartment leases	7 months
Months, maximum term of apartment leases	15 months
Future minimum rentals term, maximum	12