Investment in Unconsolidated Entities (Details 3)	3 Months Ended			0 Months Ended	12 Months Ended	3 Months Ended		12 Months Ended	3 Months Ended		0 Months Ended	3 Months Ended
	Mar. 31, 2014 USD ($)	Mar. 31, 2013 USD ($)	Dec. 31, 2013 USD ($)	Apr. 16, 2014 Klepierre EUR (€)	Dec. 31, 2013 McArthurGlen Group property	Jun. 30, 2013 McArthurGlen Group Minimum item	Mar. 31, 2014 McArthurGlen Group Ashford Designer Outlets Subsequent Event	Dec. 31, 2013 Europe property	Mar. 31, 2014 Europe Klepierre USD ($)	Mar. 31, 2013 Europe Klepierre USD ($)	Oct. 16, 2013 Europe McArthurGlen Group property	Mar. 31, 2014 Europe McArthurGlen Group USD ($)	Dec. 31, 2013 Europe McArthurGlen Group USD ($)	Oct. 16, 2013 Europe McArthurGlen Group Minimum	Oct. 16, 2013 Europe McArthurGlen Group Maximum
Schedule of Equity Method Investments
Shares owned									57,634,148
Joint venture ownership percentage							45.00%		28.90%					22.50%	90.00%
Quoted market price per share (in dollars per share)									$ 44.67
Share of net income, net of amortization of our excess investment	$ 57,423,000	$ 54,231,000							$ 4,800,000	$ 9,500,000
Total revenues									367,300,000	364,800,000
Total operating income									166,700,000	157,400,000
Total gross consideration				1,980,000,000
Group's share of total consideration				1,650,000,000
Number of joint ventures to invest in per definitive agreement						1
Consolidated net Income									52,900,000	44,300,000
Number of outlets in which interest acquired					5			5			4
Purchase price of business acquired												496,700,000
Equity investment	$ 2,347,523,000		$ 2,433,399,000									$ 516,700,000	$ 510,700,000