Equity (Details) (USD $)	1 Months Ended	3 Months Ended		9 Months Ended														0 Months Ended	1 Months Ended
	Mar. 31, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Parent [Member]	Sep. 30, 2013 Parent [Member]	Sep. 30, 2014 Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]	Sep. 30, 2014 Accumulated Distributions in Excess of Net Income [Member]	Sep. 30, 2013 Accumulated Distributions in Excess of Net Income [Member]	Sep. 30, 2013 Officers [Member]	Sep. 30, 2014 Trustees [Member]	Sep. 30, 2013 Trustees [Member]	Sep. 30, 2014 Direct Share Purchase Plan [Member]	Sep. 30, 2013 Direct Share Purchase Plan [Member]	Sep. 30, 2013 At The Market [Member]	Sep. 30, 2014 Former LCIF II Partners [Member]	Jun. 30, 2014 Office Building [Member] Philadelphia, Pennsylvania [Member] Joint Venture [Member]	Jul. 31, 2014 Office Building [Member] Philadelphia, Pennsylvania [Member] Joint Venture [Member]	Jul. 31, 2013 Industrial property [Member] Long Island City, New York [Member] Joint Venture [Member]
Equity [Line Items]
Common shares issued during period	23,000,000													1,853,988	1,052,159	3,409,927
Proceeds from issuance of common shares				$ 19,165,000	$ 306,986,000									$ 18,758,000	$ 11,600,000
Value authorized																100,000,000
Value of new stock issued during period																36,884,000
Proceeds from issuance of common stock, gross	258,336,000
Proceeds from issuance of common stock, net of issuance costs	293,855,000
Deferred compensation arrangement with individual, shares issued											1,325,000	14,000	37,500
Deferred compensation arrangement with individual, fair value of shares issued											14,098,000	142,000	399,000
OP unit equivalent in common shares				1.13
Partners capital account, units exchanged for cash																	170,193
Payments for repurchase of redeemable non-controlling interest																	1,962,000
Partners capital account, shares issued for units redeemed				11,186	169,676
Partners' capital account, redemption for common shares						56,000	887,000
OP units outstanding		3,438,000		3,438,000
Payments to acquire interest in joint venture				2,100,000	8,918,000														2,100,000	8,918,000
Real estate ownership percentage																		80.50%	87.50%
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax [Roll Forward]
Gains and Losses on Cash Flow Hedges, Beginning				4,439,000				4,439,000
Other comprehensive loss before reclassifications								(5,237,000)
Amounts of loss reclassified from accumulated other comprehensive income to interest expense								4,103,000
Gains and Losses on Cash Flow Hedges, Ending		3,305,000		3,305,000				3,305,000
Transfers from noncontrolling interests:
Net income attributable to Lexington Realty Trust shareholders		40,405,000	4,695,000	55,741,000	8,807,000				55,741,000	8,807,000
Increase (decrease) in additional paid-in-capital for redemption of noncontrolling OP units				(950,000)	887,000
Change from net income attributable to shareholders and transfers from noncontrolling interests				$ 54,791,000	$ 9,694,000