Marketable Securities and Fair Value Measurements (Marketable Securities, Available for Sale, and Derivative Financial Instruments Measured at Fair Value on Recurring Basis) (Details) (USD $) | Jun. 30, 2014 | Dec. 31, 2013 |
In Thousands, unless otherwise specified |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities, available for sale | $153,364 | $146,383 |
Equity Securities, primarily REITs [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities, available for sale | 1,621 | 10,614 |
Marco OP and OP II Units [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities, available for sale | 104,209 | 89,706 |
Corporate Bonds And Preferred Equities [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities, available for sale | 41,570 | 38,944 |
MBS [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities, available for sale | 5,964 | 7,119 |
Fair Value, Inputs, Level 1 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities, available for sale | 1,621 | 10,614 |
Fair Value, Inputs, Level 1 [Member] | Equity Securities, primarily REITs [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities, available for sale | 1,621 | 10,614 |
Fair Value, Inputs, Level 1 [Member] | Marco OP and OP II Units [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities, available for sale | ' | ' |
Fair Value, Inputs, Level 1 [Member] | Corporate Bonds And Preferred Equities [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities, available for sale | ' | ' |
Fair Value, Inputs, Level 1 [Member] | MBS [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities, available for sale | ' | ' |
Fair Value, Inputs, Level 2 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities, available for sale | 151,743 | 135,769 |
Fair Value, Inputs, Level 2 [Member] | Equity Securities, primarily REITs [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities, available for sale | ' | ' |
Fair Value, Inputs, Level 2 [Member] | Marco OP and OP II Units [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities, available for sale | 104,209 | 89,706 |
Fair Value, Inputs, Level 2 [Member] | Corporate Bonds And Preferred Equities [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities, available for sale | 41,570 | 38,944 |
Fair Value, Inputs, Level 2 [Member] | MBS [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities, available for sale | 5,964 | 7,119 |
Fair Value, Inputs, Level 3 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities, available for sale | ' | ' |
Fair Value, Inputs, Level 3 [Member] | Equity Securities, primarily REITs [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities, available for sale | ' | ' |
Fair Value, Inputs, Level 3 [Member] | Marco OP and OP II Units [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities, available for sale | ' | ' |
Fair Value, Inputs, Level 3 [Member] | Corporate Bonds And Preferred Equities [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities, available for sale | ' | ' |
Fair Value, Inputs, Level 3 [Member] | MBS [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities, available for sale | ' | ' |