Derivative Financial Instruments (Details 1) (Not Designated as Hedging Instrument [Member], Interest rate caps [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
1.25% Strike Rate Derivatives [Member]
Trust's interest rate swap
Derivative Maturity Period	May 01, 2013
Strike Rate	1.25%
Notional Amount of Hedge	$ 51,982
Cost of Hedge	196
Estimated Fair Value
Change in Cap Valuations Included in Interest Expense
1.75% Strike Rate Derivatives [Member]
Trust's interest rate swap
Derivative Maturity Period	Aug. 01, 2014
Strike Rate	1.75%
Notional Amount of Hedge	51,982
Cost of Hedge	434
Estimated Fair Value
Change in Cap Valuations Included in Interest Expense
1.00% Strike Rate Derivatives [Member]
Trust's interest rate swap
Derivative Maturity Period	Oct. 01, 2014
Strike Rate	1.00%
Notional Amount of Hedge	5,754
Cost of Hedge	174
Estimated Fair Value	1
Change in Cap Valuations Included in Interest Expense