Fair Value Measurements Fair Value Level 3 Rollforward (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended				12 Months Ended	9 Months Ended		12 Months Ended		9 Months Ended	12 Months Ended	9 Months Ended		9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012		Dec. 31, 2012	Sep. 30, 2013 Government and government sponsored entities [Member]		Dec. 31, 2012 Government and government sponsored entities [Member]		Sep. 30, 2013 Cost-method Investments [Member]	Dec. 31, 2012 Cost-method Investments [Member]	Sep. 30, 2013 Fair Value, Inputs, Level 3 [Member] Government and government sponsored entities [Member]	Dec. 31, 2011 Fair Value, Inputs, Level 3 [Member] Government and government sponsored entities [Member]	Sep. 30, 2013 Citadel Mall [Member]	Jun. 30, 2013 Citadel Mall [Member]	Dec. 31, 2012 Citadel Mall [Member]	Jun. 30, 2013 Citadel Mall [Member] Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Investments, Other																		$ 23,765		$ 45,178
Begninning balance														2,475	2,475	11,123	11,829
Redemption of TIF bonds												0				(11,002)
Net settlement									0					(4,875)
Reclassification adjustment AOCI										0		(1,542)
Transfer out of Level 3										(121)	[1]	(2,248)	[1]
Realized gain recorded in earnings									0					2,400
Ending balance														0	2,475	0	11,829
Capital expenditures																		266
Capital expenditures	81,039	[2]	78,728	[2]	277,646	[2]	232,772	[2]
Depreciation expense					(1,226)
Loss on impairment of real estate	0		(3,912)		(21,038)		(3,912)								(2,400)			(20,453)
Fair Value of Investments In Real Estate																			$ 23,900		$ 23,900

[1] (1)The TIF bonds were adjusted to their net realizable value as of December 31, 2012 and were redeemed in January 2013. The difference in estimate was recorded as a transfer to real estate assets.

[2] (3) Amounts include acquisitions of real estate assets and investments in unconsolidated affiliates. Developments in progress are included in the All Other category.