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Marketable Securities (Details) (USD $) | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2013 | Jun. 30, 2012 | Jun. 30, 2013 | Jun. 30, 2012
Schedule Of Available For Sale Securities [Line Items] |  |  |  |
Change in unrealized net gain on available-for-sale securities | $ (1,825,000) | $ 0 | $ 1,429,000 | $ 0
Macerich Interest [Member] |  |  |  |
Schedule Of Available For Sale Securities [Line Items] |  |  |  |
Macerich common shares | 535,265 |  | 535,265 |
Economic basis per share |  |  | $ 56.05 |
GAAP Cost | 30,000,000 |  | 30,000,000 |
Fair Value | 32,635,000 |  | 32,635,000 |
Closing share price (in dollars per share) | $ 60.97 |  | $ 60.97 |
Change in unrealized net gain on available-for-sale securities | $ (1,825,000) |  | $ 1,429,000 |

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