Significant Accounting Policy Other (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Commonwealth Park Property [Member]	Dec. 31, 2011 plaza escrow [Domain]
Restricted Cash and Cash Equivalents			$ 20,291	$ 1,857
Asset Impairment Charges	$ 1,813	$ 4,211

The charge against earnings resulting from the aggregate write down of all assets from their carrying value to their fair value.

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The carrying amounts of cash and cash equivalent items which are restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. This element is for unclassified presentations; for classified presentations there is a separate and distinct element.

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