Investments in Real Estate and Real Estate Under Construction - Acquisition, Pro Forma (Details) (Net Lease Strategic Assets Fund L P [Member], USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012
Net Lease Strategic Assets Fund L P [Member]
Business Acquisition [Line Items]
Gross revenues	$ 89,674
Net loss attributable to Lexington Realty Trust shareholders	(4,844)
Net loss attributable to common shareholders	$ (10,642)
Net loss per common share - basic and diluted	$ (0.07)