Lease Intangible Assets Net (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
In-Place Leases
Finite-Lived Intangible Assets [Line Items]
Net of accumulated amortization for lease intangible assets	$ 22.8	$ 20.7
Weighted average remaining life of lease intangible assets (in months)	80 months	82 months
Above Market Leases
Finite-Lived Intangible Assets [Line Items]
Net of accumulated amortization for lease intangible assets	5.8	5.2
Weighted average remaining life of lease intangible assets (in months)	67 months	70 months
Leasing Commissions
Finite-Lived Intangible Assets [Line Items]
Net of accumulated amortization for lease intangible assets	$ 5.5	$ 4.9
Weighted average remaining life of lease intangible assets (in months)	109 months	111 months