Investment in Unconsolidated Entities (Details) (USD $)	3 Months Ended			1 Months Ended		1 Months Ended				3 Months Ended			3 Months Ended					0 Months Ended	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Jan. 31, 2012 GCI	Jan. 09, 2012 GCI	Jan. 31, 2013 Shops at Mission Viejo	Mar. 31, 2013 Shops at Mission Viejo	Dec. 30, 2012 Shops at Mission Viejo	Mar. 31, 2013 Shops at Mission Viejo IMI	Mar. 31, 2013 Woodfield Mall	Mar. 31, 2013 Woodfield Mall IMI	Dec. 30, 2012 Woodfield Mall IMI	Mar. 31, 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	Mar. 31, 2013 United States joint ventures property	Dec. 31, 2012 United States joint ventures property	Mar. 31, 2013 Japan joint ventures property	Dec. 31, 2012 Japan joint ventures property	Mar. 31, 2013 Mexico joint venture property	Dec. 31, 2012 Mexico joint venture property	Mar. 31, 2013 South Korea joint ventures property	Dec. 31, 2012 South Korea joint ventures property	Mar. 31, 2013 Malaysia joint venture property	Dec. 31, 2012 Malaysia joint venture property	Jan. 09, 2012 Italy property
Real Estate Joint Ventures
Number of income-producing properties																				75	78	8	8	1	1	2	2	1	1	45
Interest in income-producing properties, under joint venture arrangements (as a percent)															28.70%
Joint venture ownership percentage							51.00%		49.00%	50.00%	50.00%
Ownership interest (as a percent)								100.00%				100.00%	28.90%	28.90%		50.00%						40.00%				50.00%
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)													$ 39.16
Excess investment in acquisition of joint venture															1,200,000,000
Income from unconsolidated entities	54,231,000	30,353,000											9,500,000
Total revenues of Klepierre													364,800,000
Operating income of Klepierre													157,400,000
Consolidated net income (loss) of Klepierre													44,300,000
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
Investment in unconsolidated entities, at equity	$ 2,001,506,000		$ 2,108,966,000																			$ 292,000,000	$ 314,200,000			$ 64,400,000	$ 62,900,000