Other Comprehensive Income of the Operating Partnership	9 Months Ended
Other Comprehensive Income of the Operating Partnership	Sep. 30, 2011
Other Comprehensive Income [Line Items]
Comprehensive Income (Loss) Note [Text Block]	Other Comprehensive Income of the Trust The functional currency of the Trust's United Kingdom operations is pounds sterling. The Trust translates the financial statements for the United Kingdom operations into US dollars. Gains and losses resulting from this translation do not impact the results of operations and are included in accumulated other comprehensive loss as a separate component of shareholders' equity. A proportionate amount of gain or loss is allocated to noncontrolling interest-common units. Accumulated other comprehensive loss consists solely of the foreign currency translation adjustments described above. Other comprehensive loss for the three months ended September 30, 2011 was $2.2 million and for the nine months ended September 30, 2011 was $0.1 million. Other comprehensive income for the three months ended September 30, 2010 was $3.7 million and for the nine months ended September 30, 2010 was a loss of $2.0 million. Upon sale or upon complete or substantially complete liquidation of the Trust's foreign investment, the gain or loss on the sale will include the cumulative translation adjustments that have been previously recorded in accumulated other comprehensive income (loss) and noncontrolling interest-common units. Total comprehensive income for the three months ended September 30, 2011 was $39.4 million and for the nine months ended September 30, 2011 was $169.4 million. Total comprehensive income for the three months ended September 30, 2010 was $44.7 million and for the nine months ended September 30, 2010 was $114.8 million.
Liberty Property Limited Partnership [Member]
Other Comprehensive Income [Line Items]
Comprehensive Income (Loss) Note [Text Block]	Other Comprehensive Income of the Operating Partnership The functional currency of the Operating Partnership’s United Kingdom operations is pounds sterling. The Operating Partnership translates the financial statements for the United Kingdom operations into US dollars. Gains and losses resulting from this translation do not impact the results of operations and are included in general partner’s equity – common units and limited partners’ equity-common units. Other comprehensive loss for the three months ended September 30, 2011 was $2.2 million and for the nine months ended September 30, 2011 was $0.1 million. Other comprehensive income for the three months ended September 30, 2010 was $3.7 million and for the nine months ended September 30, 2010 was a loss of $2.0 million. Upon sale or upon complete or substantially complete liquidation of the Operating Partnership's foreign investment, the gain or loss on the sale will include the cumulative translation adjustments that have been previously recorded in general partner’s equity-common units and limited partners’ equity – common units. Total comprehensive income for the three months ended September 30, 2011 was $39.4 million and for the nine months ended September 30, 2011 was $169.4 million. Total comprehensive income for the three months ended September 30, 2010 was $44.7 million and for the nine months ended September 30, 2010 was $114.8 million .

The entire disclosure for comprehensive income. Includes, but is not limited to, the following: 1) the amount of income tax expense or benefit allocated to each component of other comprehensive income, including reclassification adjustments, 2) the reclassification adjustments for each classification of other comprehensive income and 3) the ending accumulated balances for each component of comprehensive income. Components of comprehensive income include: (1) foreign currency translation adjustments; (2) gains (losses) on foreign currency transactions that are designated as, and are effective as, economic hedges of a net investment in a foreign entity; (3) gains (losses) on intercompany foreign currency transactions that are of a long-term-investment nature, when the entities to the transaction are consolidated, combined, or accounted for by the equity method in the reporting enterprise's financial statements; (4) change in the market value of a futures contract that qualifies as a hedge of an asset reported at fair value; (5) unrealized holding gains (losses) on available-for-sale securities and that resulting from transfers of debt securities from the held-to-maturity category to the available-for-sale category; (6) a net loss recognized as an additional pension liability not yet recognized as net periodic pension cost; and (7) the net gain (loss) and net prior service cost or credit for pension plans and other postretirement benefit plans.

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+ Details