Derivative Instruments and Hedging Activities (Details 1) - Cash Flow Hedging [Member] - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Derivative instruments gain (loss) in financial statements
Gain (loss) recognized in OCI (effective portion)	$ (231,000)	$ (7,194,000)	$ (7,703,000)	$ (11,454,000)
Gain (loss) reclassified from accumulated OCI, effective amount	(9,420,000)	(10,417,000)	(19,367,000)	(20,854,000)
Gain (loss) reclassified from accumulated OCI, ineffective amount	3,000	0	(12,000)	(3,666,000)
Interest rate caps and interest rate swaps [Member]
Derivative instruments gain (loss) in financial statements
Gain (loss) recognized in OCI (effective portion)	(231,000)	(7,194,000)	(7,703,000)
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	(9,344,000)	(9,414,000)	(18,301,000)
Gain (loss) reclassified from accumulated OCI, ineffective amount	3,000	0	(11,000)
Interest rate caps and interest rate swaps [Member] | Net Gain on Change in Control of Interests [Member]
Derivative instruments gain (loss) in financial statements
Gain (loss) reclassified from accumulated OCI, effective amount	900,000		900,000
Gain (loss) reclassified from accumulated OCI, ineffective amount	0		0
Interest rate caps and interest rate swaps [Member] | Earnings (loss) from Unconsolidated Entities, Gross of Tax [Member]
Derivative instruments gain (loss) in financial statements
Gain (loss) reclassified from accumulated OCI, effective amount	(976,000)		(1,966,000)
Gain (loss) reclassified from accumulated OCI, ineffective amount	$ 0		$ (1,000)
Interest rate caps, interest rate swaps and treasury options [Member]
Derivative instruments gain (loss) in financial statements
Gain (loss) recognized in OCI (effective portion)				(11,454,000)
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				(18,851,000)
Gain (loss) reclassified from accumulated OCI, ineffective amount				0
Interest rate caps, interest rate swaps and treasury options [Member] | Earnings (loss) from Unconsolidated Entities, Gross of Tax [Member]
Derivative instruments gain (loss) in financial statements
Gain (loss) reclassified from accumulated OCI, effective amount		(1,003,000)		(2,003,000)
Gain (loss) reclassified from accumulated OCI, ineffective amount		$ 0		0
Interest rate caps, interest rate swaps and treasury options [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)