Fair Value Measurements (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Fair value assets measured on non recurring basis unobservable input reconciliation
Total impairment losses, investment properties	$ 39,942	[1]	$ 47,015	[2]	$ 228,370	[3]	$ 53,842	[4]
Fair Value, Measurements, Nonrecurring [Member]
Fair value assets measured on non recurring basis unobservable input reconciliation
Total impairment losses, investment properties					228,370		53,842
Total impairment losses, investment in unconsolidated entities					6,532		4,200
Total impairment losses					234,902		58,042
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair value assets measured on non recurring basis unobservable input reconciliation
Fair value measurements, investment properties					235,443		104,356
Fair value measurements, investment in unconsolidated entities					36,335		16,914
Fair value measurements, total					$ 271,778		$ 121,270

[1] Total provision for asset impairment included $11,724 related to three retail properties, $26,175 related to two lodging properties, and $2,043 related to three non-core properties.

[2] Total provision for asset impairment included $34,345 related to two retail properties and $12,670 related to four non-core properties.

[3] Total provision for asset impairment included $24,540 related to five retail properties, $26,175 related to two lodging properties, $177,655 related to ten non-core properties.

[4] The total provision for asset impairment relates to $37,017 related to three retail properties, and $16,825 related to five non-core properties.