Risk Management and Use of Financial Instruments (Fair Values of Derivative Financial Instruments) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Other Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	$ 51,548	$ 51,548
Derivative, Fair Value, Net	315	767
Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	377,062	377,062
Derivative, Fair Value, Net	(2,716)	(2,188)
3.300% Interest Rate Swap Maturing January 30, 2021 [Member] | Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Other Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	25,774	25,774
Derivative, Fixed Interest Rate	3.30%
Derivative, Fair Value, Net	252	549
3.090% Interest Rate Swap Maturing October 30, 2019 [Member] | Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Other Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	25,774	25,774
Derivative, Fixed Interest Rate	3.09%
Derivative, Fair Value, Net	63	218
3.623% Interest Rate Swap Maturing February 1, 2019 [Member] | Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	200,000	200,000
Derivative, Fixed Interest Rate	3.623%
Derivative, Fair Value, Net	(1,195)	(545)
2.703% Interest Rate Swap Maturing February 1, 2016 [Member] | Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	77,000	77,000
Derivative, Fixed Interest Rate	2.703%
Derivative, Fair Value, Net	(825)	(887)
2.470% Interest Rate Swap Maturing February 1, 2015 [Member] | Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	50,000	50,000
Derivative, Fixed Interest Rate	2.47%
Derivative, Fair Value, Net	(250)	(283)
2.513% Interest Rate Swap Maturing May 1, 2015 [Member] | Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	23,000	23,000
Derivative, Fixed Interest Rate	2.513%
Derivative, Fair Value, Net	(150)	(162)
2.750% Interest Rate Swap Maturing September 30, 2017 [Member] | Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	27,062	27,062
Derivative, Fixed Interest Rate	2.75%
Derivative, Fair Value, Net	$ (296)	$ (311)