Derivative and Hedging Activities (Effect of Derivative Instruments on the Consolidated Statement of Operations and Comprehensive Income) (Details) (Cash Flow Hedging [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Effect of derivative instruments on the Consolidated Statement of Operations and Comprehensive Income [Abstract]
Amount of gain or (loss) recognized in OCI on derivative (effective portion)	$ (396)	$ (1,790)	$ 10,414	$ (6,473)
Amount of gain or (loss) reclassified from AOCI into income (effective portion)	(1,589)	(1,737)	(4,703)	(5,150)
Realized losses on settled cash flow hedges	(151)	(151)	(454)	(641)
Interest rate contract – consolidated subsidiary | Other comprehensive income [Member]
Effect of derivative instruments on the Consolidated Statement of Operations and Comprehensive Income [Abstract]
Amount of gain or (loss) recognized in OCI on derivative (effective portion)	(67)	(897)	6,375	(3,671)
Interest rate contract – consolidated subsidiary | Interest expense [Member]
Effect of derivative instruments on the Consolidated Statement of Operations and Comprehensive Income [Abstract]
Amount of gain or (loss) reclassified from AOCI into income (effective portion)	(812)	(802)	(2,406)	(2,380)
Realized losses on settled cash flow hedges	(151)	(151)	(454)	(453)
Interest rate contracts - UJVs [Member] | Other comprehensive income [Member]
Effect of derivative instruments on the Consolidated Statement of Operations and Comprehensive Income [Abstract]
Amount of gain or (loss) recognized in OCI on derivative (effective portion)	(329)	(893)	4,039	(2,802)
Interest rate contracts - UJVs [Member] | Equity Method Investments [Member]
Effect of derivative instruments on the Consolidated Statement of Operations and Comprehensive Income [Abstract]
Amount of gain or (loss) reclassified from AOCI into income (effective portion)	(777)	(935)	(2,297)	(2,770)
Realized losses on settled cash flow hedges				$ (188)