Cash Flow Information - Additional Information (Detail) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2015 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)
Other Significant Noncash Transactions [Line Items]
Cash paid for interest		$ 56.2	$ 55.8
Net of capitalized interest		1.6	0.5
Line of credit facilities gross borrowings		290.0	140.0
Line of credit facilities gross repayments		$ 230.0	$ 270.0
Springfield Town Center [Member]
Other Significant Noncash Transactions [Line Items]
Other significant noncash transaction, consideration given, OP Units	6,250,000
Other Significant Noncash Transaction, Value of Consideration Given	$ 145.2