Investments in Partially Owned Entities - Summary of Financial Information (Detail) (Senior Management Concepts Senior Living Portfolio [Member], USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Senior Management Concepts Senior Living Portfolio [Member]
Investment Holdings [Line Items]
Assets	$ 10.3		$ 10.3		$ 10.8
Liabilities	15.1		15.1		14.9
Equity	(4.8)		(4.8)		(4.1)
Revenues	0.8	0.8	1.6	1.7
Expenses	1.0	0.9	1.9	1.8
Net loss	$ (0.2)	$ (0.1)	$ (0.3)	$ (0.1)