Investments in Unconsolidated Entities - Additional Information (Detail)	1 Months Ended		9 Months Ended	12 Months Ended				1 Months Ended			9 Months Ended			9 Months Ended		1 Months Ended			2 Months Ended	9 Months Ended																										9 Months Ended			1 Months Ended		1 Months Ended		1 Months Ended									1 Months Ended					1 Months Ended		1 Months Ended						1 Months Ended
	Jan. 31, 2009 USD ($)	Oct. 31, 2006 USD ($)	Sep. 30, 2012 USD ($) Store Hospital State Physician	Dec. 31, 2011 USD ($)	Nov. 07, 2012 sqft	Mar. 24, 2011 USD ($)	Dec. 29, 2010 USD ($)	Aug. 31, 2011 Duke joint venture paid CBRE Capital Markets, LLC [Member] USD ($)	Aug. 25, 2011 Duke joint venture paid CBRE Capital Markets, LLC [Member] USD ($)	Aug. 16, 2011 Duke joint venture paid CBRE Capital Markets, LLC [Member] USD ($)	Sep. 30, 2012 CBRE Strategic Partners Asia [Member] USD ($) Property	Dec. 31, 2011 CBRE Strategic Partners Asia [Member] USD ($)	Sep. 30, 2012 CBRE Strategic Partners Asia [Member] Japan [Member] Property	Sep. 30, 2012 CBRE Strategic Partners Asia [Member] China [Member] Property	Sep. 30, 2010 CBRE Strategic Partners Asia [Member] China [Member] Property	Aug. 31, 2012 Duke Joint Venture [Member] USD ($)	Aug. 31, 2011 Duke Joint Venture [Member] USD ($)	Apr. 30, 2011 Duke Joint Venture [Member] USD ($)	Mar. 31, 2011 Duke Joint Venture [Member] USD ($)	Sep. 30, 2012 Duke Joint Venture [Member] USD ($) Property		Dec. 31, 2011 Duke Joint Venture [Member] USD ($)	Sep. 12, 2011 Duke Joint Venture [Member] USD ($)	Aug. 25, 2011 Duke Joint Venture [Member] USD ($)	Aug. 16, 2011 Duke Joint Venture [Member] USD ($) SecurityLoan	Aug. 08, 2011 Duke Joint Venture [Member] USD ($)	Aug. 04, 2011 Duke Joint Venture [Member] USD ($)	Apr. 28, 2011 Duke Joint Venture [Member] USD ($) sqft	Mar. 24, 2011 Duke Joint Venture [Member] USD ($) Property	May 05, 2008 Duke Joint Venture [Member] USD ($) Industry	Sep. 30, 2012 Duke Joint Venture [Member] Florida [Member] Property	Sep. 30, 2012 Duke Joint Venture [Member] Ohio [Member] Property	Sep. 30, 2012 Duke Joint Venture [Member] North Carolina [Member] Property	Sep. 30, 2012 Duke Joint Venture [Member] Texas [Member] Property	Sep. 30, 2012 Duke Joint Venture [Member] Arizona [Member] Property	Sep. 30, 2012 Duke Joint Venture [Member] Illinois [Member] Property	Sep. 30, 2012 Duke Joint Venture [Member] Indiana [Member ] Property	Sep. 30, 2012 Duke Joint Venture [Member] Minnesota [Member] Property	Sep. 30, 2012 Duke Joint Venture [Member] Missouri [Member] Property	Sep. 30, 2012 Duke Joint Venture [Member] Tennessee [Member] Property	Aug. 08, 2011 Duke Joint Venture [Member] Duke joint venture paid CBRE Capital Markets, LLC [Member] USD ($)	Aug. 25, 2011 Duke Joint Venture [Member] Principal Life Insurance Company [Member] USD ($) SecurityLoan	Sep. 12, 2011 Duke Joint Venture [Member] John Hancock Life Insurance Company [Member] USD ($) SecurityLoan	Sep. 12, 2011 Duke Joint Venture [Member] John Hancock Life Insurance Company [Member] Minimum [Member]	Sep. 12, 2011 Duke Joint Venture [Member] John Hancock Life Insurance Company [Member] Maximum [Member]	Sep. 30, 2012 Duke Joint Venture [Member] Amec Paragon Inc [Member] sqft	Aug. 08, 2011 Duke Joint Venture [Member] Fairfield Distribution Center IX [Member] USD ($)	Aug. 08, 2011 Duke Joint Venture [Member] West Lake at Conway [Member] USD ($)	Aug. 31, 2011 Duke Joint Venture [Member] Easton III property [Member]	Aug. 16, 2011 Duke Joint Venture [Member] Easton III property [Member] USD ($)	Aug. 31, 2011 Duke Joint Venture [Member] Point West I property [Member]	Aug. 16, 2011 Duke Joint Venture [Member] Point West I property [Member] USD ($)	Aug. 31, 2011 Duke Joint Venture [Member] Atrium I property [Member]	Aug. 16, 2011 Duke Joint Venture [Member] Atrium I property [Member] USD ($)	Aug. 25, 2011 Duke Joint Venture [Member] Sam Houston Crossing I Property [Member]	Aug. 25, 2011 Duke Joint Venture [Member] Sam Houston Crossing I Property [Member] Principal Life Insurance Company [Member] Minimum [Member]	Aug. 25, 2011 Duke Joint Venture [Member] Sam Houston Crossing I Property [Member] Principal Life Insurance Company [Member] Maximum [Member]	Aug. 25, 2011 Duke Joint Venture [Member] McAuley Place Property [Member] Principal Life Insurance Company [Member]	Aug. 25, 2011 Duke Joint Venture [Member] McAuley Place Property [Member] Principal Life Insurance Company [Member] Minimum [Member]	Aug. 25, 2011 Duke Joint Venture [Member] McAuley Place Property [Member] Principal Life Insurance Company [Member] Maximum [Member]	May 05, 2008 Duke Joint Venture [Member] Leased office building [Member] USD ($)	Sep. 30, 2008 Afton Ridge Joint Venture [Member] USD ($)	Sep. 30, 2012 Afton Ridge Joint Venture [Member] USD ($)	Dec. 31, 2011 Afton Ridge Joint Venture [Member] USD ($)	Sep. 18, 2008 Afton Ridge Joint Venture [Member] USD ($) acre	Sep. 18, 2008 Afton Ridge Joint Venture [Member] Ck Afton Ridge Shopping Center LLC [Member] sqft	Sep. 30, 2008 Afton Ridge Joint Venture [Member] Super Target [Member] sqft	Sep. 18, 2008 Afton Ridge Joint Venture [Member] Metropolitan Life Insurance Company [Member] USD ($)	Mar. 31, 2012 UK JV [Member] USD ($)	Sep. 30, 2012 UK JV [Member] USD ($)	Dec. 31, 2011 UK JV [Member] USD ($)	Jun. 10, 2010 UK JV [Member] USD ($)	Jun. 10, 2010 UK JV [Member] GBP (£)	Jun. 10, 2010 UK JV [Member] Goodman Group [Member]	Jul. 27, 2012 European JV [Member] USD ($)	Jul. 27, 2012 European JV [Member] GBP (£)	Dec. 31, 2011 European JV [Member] USD ($)	Oct. 31, 2010 European JV [Member] USD ($)	Sep. 30, 2012 European JV [Member] USD ($)	Jun. 10, 2010 European JV [Member] USD ($)	Jun. 10, 2010 European JV [Member] GBP (£)	Jun. 10, 2010 European JV [Member] Goodman Group [Member]
Schedule of Investments [Line Items]
Capital commitment											$ 20,000,000
Period for extension of final capital commitment											57 months
Capital commitment funded	3,000,000,000	2,000,000,000									17,526,000
Aggregate capital commitments											394,203,000
Aggregate capital commitment period											8 years
Extension in agreement period											Up to two one-year periods
Aggregate investor commitments											394,203,000
Interest owned											5.07%																			80.00%													5.24%												4.42%			3.98%							90.00%															80.00%	80.00%
Number of properties in which ownership interests acquired											10		5	5
Number of properties sold														1	2
Maximum percentage of ownership			20.00%
Acquisition cost																													342,800,000	248,900,500												60,500,000																							45,000,000								400,000,000								400,000,000
Number of bulk industrial																														6
Purchase price consideration of leased office building																													274,240,000																																37,111,000
Purchase commitment																														282,400,000
Ownership percentage held by other party																														20.00%																																				10.00%								20.00%								20.00%
Acquisition of properties																				37									13		10	8	4	4	2	2	2	2	2	1
Unsecured term loan						275,000,000																							275,000,000
Term Loan obligation attributable to reporting entity																													220,000,000													20,000,000	125,000,000
Term Loan period																													6 months															10 years	30 years											10 years	30 years		7 years	25 years								5 years
Term Loan extension description																													Two six-month extension options
Interest rate																													2.50%																																							5.70%
Term Loan origination fee																			1,650,000
Percentage of leased					10000.00%															100.00%
Net rentable square feet					280,577																							604,678																																						470,288
Net rentable area expansion under the expansion agreement																												1,009,351																																						296,388
Remaining property leased																												100.00%
Lease expiration																		September 2021		06/2013
Construction supervision fee																		254,000
Anticipated lease expansion cost																												21,609,000
Cash contributions to Duke joint venture in connection with Buckeye Expansion Agreement																												17,287,000
Contribution for 80% share			12,793,000	149,132,000												31,200,000																																																					10,764,000								62,559,000	18,672,000
Total value of Duke joint venture																											39,000,000
Net proceeds from the financing totaling used to pay Term Loan																											13,818,000
Duke joint venture closed on loans																				473,919,000	[1]					14,425,000																					4,675,000	9,750,000
Term Loan total amount paid																	52,818,000
Unsecured Long Term Debt Outstanding																																									222,182,000
Amount of loan closed																									43,400,000																	25,000,000	156,250,000
Secured loan									179,482,000	222,182,000																																								6,900,000		11,800,000		24,700,000														25,500,000
Number of loan closed																									3																	2	5
Interest rate swap																																																		3.95%		3.41%		3.775%
Maturity Date																																																	Jan. 31, 2019		Dec. 06, 2016		May 31, 2018
Reduction in outstanding balance								154,482,000								179,482,000
Repayment of loans																							154,482,000	25,000,000	42,700,000
Percentage of contribution share																																										80.00%	80.00%
Percentage of loan-to-cost on total allocated acquisition costs of the properties																				41.30%
Purchase price consideration of leased office building																				1,023,241,000	[2]
Net rentable square feet																																														50,000
Number of hospitals			5
Number of physician practices			38
Number of stores			850
Number of states			48
Acquisition fee																				10,143,599	[3]																																									450,000
Percentage of leased property																																																																		99.00%
Area of acre master planned mixed-use development																																																																	260
Area not owned by company																																																																			173,900
Additional Term Loan Period																																																																				12 months
Investments in Unconsolidated Entities			487,996,000	537,631,000			410,062,000				7,779,000	8,381,000								350,896,000		377,145,000																																									17,405,000	18,274,000						37,543,000	26,590,000	26,180,000					107,241,000		74,373,000	26,802,000
Extinguishment of debt amount																																																																											38,390,000	31,100,000
Exchange rate																																																																											1.2344	1.0000
Exchange rate of pro rata share																																																																											$ 30,712,000
Percentage of pro rata share																																																																											80.00%	80.00%
Fixed interest rate																																																																											2.39%	2.39%

[1] Approximate debt financing net of amortization.

[2] Approximate total purchase price including the AllPoints at Anson Bldg. 1 and Buckeye Logistics Center expansion costs, exclusive of closing costs, paid by the Duke joint venture for each of these properties.

[3] Acquisition fees paid to our former investment advisor are included in the total acquisition cost for the properties acquired prior to January 1, 2009, but are included as acquisition expenses for properties acquired subsequent to December 31, 2008.