Derivative Instruments and Hedging Activities (Details 2) (Cash Flow Hedging, USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Derivative Instruments and Hedging Activities
Gain (loss) recognized in OCI on derivative (effective portion)	$ (225,000)	$ (277,000)	$ (986,000)	$ (277,000)
Amount reclassified from OCI into income (effective portion)	228,000		645,000
Unrealized loss held in accumulated OCI to be reclassified to earnings			1,200,000
Estimated period for the transfer of unrealized loss to earnings			12 months
Interest expense
Derivative Instruments and Hedging Activities
Amount reclassified from OCI into income (effective portion)	228,000		645,000
Interest rate caps
Derivative Instruments and Hedging Activities
Gain (loss) recognized in OCI on derivative (effective portion)	17,000	(277,000)	(3,000)	(277,000)
Interest rate swaps
Derivative Instruments and Hedging Activities
Gain (loss) recognized in OCI on derivative (effective portion)	$ (242,000)		$ (983,000)