Investments in Real Estate Ventures (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2013 USD ($) investment	Sep. 30, 2012 USD ($)	Sep. 30, 2013 USD ($) investment	Sep. 30, 2012 USD ($)	Dec. 31, 2012 USD ($)	Sep. 30, 2013 LaSalle Investment Company I [Member] USD ($)	Sep. 30, 2013 LaSalle Investment Company I [Member] EUR (€)	Sep. 30, 2013 LaSalle Investment Company II [Member] USD ($)	Dec. 31, 2012 LaSalle Investment Company II [Member] USD ($)	Sep. 30, 2012 LaSalle Investment Company II [Member] USD ($)	Dec. 31, 2011 LaSalle Investment Company II [Member] USD ($)	Sep. 30, 2013 Variable Interest Entities [Member] USD ($)	Dec. 31, 2012 Variable Interest Entities [Member] USD ($)
Schedule of Equity Method Investments [Line Items]
Total investments in real estate ventures	$ 287,747,000		$ 287,747,000		$ 268,107,000							$ 6,000,000	$ 6,700,000
Number of separate property or fund co-investments	50		50
Minimum ownership percentage in real estate ventures (in hundredths)	1.00%		1.00%
Maximum ownership percentage in real estate ventures (in hundredths)	15.00%		15.00%
Number of investment vehicles to facilitate the majority of our co-investment activity	2		2
Entity's maximum potential unfunded commitment						5,100,000	3,700,000
Unfunded capital commitments to the underlying funds for future funding of co-investments								192,800,000
Partnership ownership interest (in hundredths)						47.85%	47.85%	48.78%
Entity's share of unfunded capital commitments for future funding of co-investments								94,100,000
Percentage ownership interest held by other parties (in hundredths)						52.15%	52.15%	51.22%
Revolving credit facility, maximum capacity								60,000,000
Entity's maximum exposure, assuming facility was fully drawn								29,300,000
Outstanding borrowings on the revolving credit facility								6,700,000
Maximum loss exposure, amount	64,800,000		64,800,000					128,600,000
Impairment [Abstract]
Impairment charges	800,000	1,500,000	3,000,000	5,900,000
Minimum expected period for vehicle to draw down on commitment	3 years		3 years
Maximum expected period for vehicle to draw down on commitment	5 years		5 years
Fair Value [Abstract]
Fair value investments at beginning of the period			63,579,000	23,169,000				61,100,000	49,200,000	43,600,000	12,700,000
Investments			13,392,000	54,173,000
Distributions			(2,727,000)	(1,500,000)
Net fair value gain	4,000,000	300,000	3,320,000	1,062,000
Foreign currency translation adjustments, net			(2,468,000)	807,000
Fair value investments at end of the period	$ 75,096,000	$ 77,711,000	$ 75,096,000	$ 77,711,000				$ 61,100,000	$ 49,200,000	$ 43,600,000	$ 12,700,000