Investment in Unconsolidated Entities (Details) (USD $)	3 Months Ended		6 Months Ended				1 Months Ended		1 Months Ended				6 Months Ended					6 Months Ended					0 Months Ended	12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Jun. 30, 2013 McArthurGlen Group	Jan. 31, 2012 GCI	Jan. 09, 2012 GCI	Jan. 31, 2013 Shops at Mission Viejo	Jun. 30, 2013 Shops at Mission Viejo	Dec. 30, 2012 Shops at Mission Viejo	Jun. 30, 2013 Shops at Mission Viejo IMI	Jun. 30, 2013 Woodfield Mall	Jun. 30, 2013 Woodfield Mall IMI	Dec. 30, 2012 Woodfield Mall IMI	Jun. 30, 2013 Value Retail PLC property	Dec. 31, 2012 Value Retail PLC	Jun. 30, 2013 Klepierre	May 21, 2012 Klepierre	Mar. 14, 2012 Klepierre	Jan. 06, 2012 Del Amo Fashion Center	Mar. 22, 2012 The Mills acquisition property	Mar. 22, 2012 The Mills acquisition SPG-FCM property	Dec. 31, 2012 The Mills acquisition SPG-FCM	Jun. 30, 2013 United States joint ventures property	Dec. 31, 2012 United States joint ventures property	Jun. 30, 2013 Japan joint ventures property	Dec. 31, 2012 Japan joint ventures property	Jun. 30, 2013 Mexico joint venture property	Dec. 31, 2012 Mexico joint venture property	Jun. 30, 2013 South Korea joint ventures property	Dec. 31, 2012 South Korea joint ventures property	Jun. 30, 2013 Malaysia joint venture property	Dec. 31, 2012 Malaysia joint venture property	Jan. 09, 2012 Italy property	Jun. 30, 2013 Canada McArthurGlen Group property	Jun. 30, 2013 Europe	Jun. 30, 2013 Europe Value Retail PLC property
Real Estate Joint Ventures and Investments
Number of income-producing properties																3									74	78	9	8	1	1	2	2	1	1	45
Interest in income-producing properties, under joint venture arrangements (as a percent)																				28.70%																	28.90%
Joint venture ownership percentage										51.00%		49.00%	50.00%	50.00%
Ownership interest (as a percent)						50.00%					100.00%				100.00%			28.90%	28.90%		50.00%						40.00%				50.00%					45.00%
Aggregate face amount of mortgage notes									$ 295,000,000				$ 425,000,000
Weighted average interest rates on mortgage notes (as a percent)									3.61%				4.50%
Amount of distribution received from proceeds of financing in joint venture									149,700,000
Number of properties in which additional interest is acquired																							26
Number of remaining unconsolidated properties																							16
Number of income-producing properties acquired																						9
Cost of acquisition including assumption of debt																				2,000,000,000			1,500,000,000
Debt obligation related to consolidated properties disposed of																							562,100,000
Trust preferred securities retired																							100,000,000
Related party debt obligations extinguished during the period																							558,400,000
Mortgage indebtedness assumed																							2,600,000,000
Gain due to acquisition of controlling interest																								488,700,000
Other than temporary impairment charge																								22,400,000
Purchase price of business acquired																					50,000,000
Number of shares owned in acquired entity																		57,634,148
Quoted market price of shares owned in acquired entity (in dollars per share)																		$ 39.47
Excess investment in acquisition of joint venture																				1,200,000,000
Share of net income, net of amortization of our excess investment	56,516,000	29,132,000	110,747,000	59,484,000														23,300,000
Total revenues of Klepierre																		725,600,000
Operating income of Klepierre																		282,900,000
Consolidated net income (loss) of Klepierre																		97,900,000
Number of development projects																																				1
Investment in unconsolidated entities, at equity	1,958,503,000		1,958,503,000		2,108,966,000	38,700,000																					275,000,000	314,200,000			67,100,000	62,900,000
Number of luxury outlets owned and operated																																						9
Carrying value of investments under the cost method																115,300,000	95,500,000
Proceeds from sale of interest in joint venture							375,800,000
Gain (loss) upon acquisition of controlling interest, and on sale or disposal of assets and interests in unconsolidated entities, net							28,800,000
Accumulated losses reclassified								$ 39,500,000