Fair Values of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Financial Liabilities [Abstract]
Interest rate swap agreements	$ 16,285	$ 11,134
Carrying Amount [Member]
Financial Assets [Abstract]
Cash and cash equivalents	81,856	75,183
Financial Liabilities [Abstract]
Mortgage notes payable	605,889	752,414
Notes payable to banks	262,000	132,322
Interest rate swap agreements	16,285	11,134
Fair Value [Member]
Financial Assets [Abstract]
Cash and cash equivalents	81,856	75,183
Financial Liabilities [Abstract]
Mortgage notes payable	623,604	761,942
Notes payable to banks	254,215	125,494
Interest rate swap agreements	$ 16,285	$ 11,134

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Company may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months.

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Derivative instrument obligations meeting the definition of a liability which the Company is a party to as of the balance sheet date.

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- Definition

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