Segment Disclosure - Capital Expenditures (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Capital Expenditures
Capital expenditures	$ 169,038	$ 399,584
Domestic Industrial Properties Continuing Operations [Member]
Capital Expenditures
Capital expenditures	124,852	45,604
Domestic Office Properties Continuing Operations [Member]
Capital Expenditures
Capital expenditures	520	353,658
International Office/Retail Properties [Member]
Capital Expenditures
Capital expenditures	644	90
Non-Segment Assets [Member]
Capital Expenditures
Capital expenditures	527	232
Variable Interest Entity [Member]
Capital Expenditures
Capital expenditures	$ 42,495	$ 0