Equity (Narrative) (Details) (USD $) Share data in Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Stockholders' Equity Attributable to Parent [Abstract]
Noncontrolling interest, ownership percentage by noncontrolling owners	17.00%
Number of Shares of Common Stock issued upon redemption of one OP unit	1
Ownership percentage in joint venture	66.67%
Stock Issued During Period, Shares, New Issues	0	6,900
Net proceeds from ATM common stock issuances		$ 128,300,000
Number of operating partnership units converted to shares of common stock	1,300	26
Non-cash amortization of stock-based compensation	1,562,000	1,449,000
Capitalized equity compensation	101,000	120,000
Value of Grants Fully Vested At The Time Of Grant		$ 3,000,000

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Number of Shares of Common Stock issued upon redemption of one OP unit

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Proceeds from issuance of ATM common stocks.

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Value of Grants Fully Vested At The Time Of Grant

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Represents the compensation cost capitalized during the period arising from equity-based compensation arrangements (for example, shares of stock, units, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

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The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

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The number of shares issued during the period upon the conversion of units. An example of a convertible unit is an umbrella partnership real estate investment trust unit (UPREIT unit).

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Number of new stock issued during the period.

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