Subsequent Events (Detail) (USD $)		1 Months Ended	0 Months Ended
	Jun. 30, 2012	Jul. 25, 2012 Subsequent Event [Member] Six Point Two Five Percent Senior Note Due 2013 [Member]	Jul. 13, 2012 Fountain Square [Member] Subsequent Event [Member] sqft
Net rentable square feet			811,000
Acquisition aggregate purchase price			$ 385,000,000
Mortgage loan on acquisition of property			211,300,000
Percentage of ownership interest			50.00%
Interest on mortgage loan paid in cash			87,000,000
Interest at a fixed rate		6.25%	5.71%
Mortgage loan maturity date			Oct. 01, 2016
Partner's interest acquisition price			102,000,000
Fixed price option rights expiry date			Jan. 31, 2016
Aggregate principal amount	$ 1,197,500,000	$ 225,000,000
Percentage found in make whole provision		0.35%