Derivative Instruments and Hedging Activities (Details 1) (Cash Flow Hedging [Member], USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Derivative instruments gain (loss) in financial statements
Gain (loss) recognized in OCI (effective portion)	$ 2,645,000	$ 23,433,000	$ 8,010,000	$ 31,689,000
Gain (loss) reclassified from accumulated OCI, effective amount	(579,000)	(968,000)	(1,391,000)	(2,001,000)
Gain (loss) reclassified from accumulated OCI, ineffective amount	0	2,000	(3,666,000)	5,000
Interest rate caps and interest rate swaps [Member]
Derivative instruments gain (loss) in financial statements
Gain (loss) recognized in OCI (effective portion)	2,645,000		8,010,000
Interest rate caps and interest rate swaps [Member] | Interest expense [Member]
Derivative instruments gain (loss) in financial statements
Gain (loss) reclassified from accumulated OCI, effective amount	(564,000)		(1,361,000)
Gain (loss) reclassified from accumulated OCI, ineffective amount	0		0
Interest rate swap [Member]
Derivative instruments gain (loss) in financial statements
Gain (loss) recognized in OCI (effective portion)			0
Interest rate swap [Member] | Discontinued operations [Member]
Derivative instruments gain (loss) in financial statements
Gain (loss) reclassified from accumulated OCI, effective amount			0
Gain (loss) reclassified from accumulated OCI, ineffective amount			(3,666,000)
Interest rate swaps [Member]
Derivative instruments gain (loss) in financial statements
Gain (loss) recognized in OCI (effective portion)	0		0
Interest rate swaps [Member] | Equity in earnings [Member]
Derivative instruments gain (loss) in financial statements
Gain (loss) reclassified from accumulated OCI, effective amount	(15,000)		(30,000)
Gain (loss) reclassified from accumulated OCI, ineffective amount	0		0
Interest rate caps, interest rate swaps and treasury options [Member]
Derivative instruments gain (loss) in financial statements
Gain (loss) recognized in OCI (effective portion)		23,433,000		31,689,000
Interest rate caps, interest rate swaps and treasury options [Member] | Interest expense [Member]
Derivative instruments gain (loss) in financial statements
Gain (loss) reclassified from accumulated OCI, effective amount		(954,000)		(1,923,000)
Gain (loss) reclassified from accumulated OCI, ineffective amount		0		0
Interest rate caps, interest rate swaps and treasury options [Member]
Derivative instruments gain (loss) in financial statements
Gain (loss) recognized in OCI (effective portion)		0		0
Interest rate caps, interest rate swaps and treasury options [Member] | Equity in earnings [Member]
Derivative instruments gain (loss) in financial statements
Gain (loss) reclassified from accumulated OCI, effective amount		(14,000)		(78,000)
Gain (loss) reclassified from accumulated OCI, ineffective amount		$ 2,000		$ 5,000