Organization (Details)	Mar. 31, 2015 state item property	Jan. 15, 2015	Dec. 31, 2014
Real Estate Properties
Joint venture ownership percentage	18.30%
Klepierre
Real Estate Properties
Joint venture ownership percentage			28.90%
McArthurGlen Group
Real Estate Properties
Number of properties	5
U.S. and Puerto Rico
Real Estate Properties
Number of properties	209
Number of U.S. states containing property locations | state	37
U.S. and Puerto Rico | Malls
Real Estate Properties
Number of properties	110
U.S. and Puerto Rico | Premium Outlets
Real Estate Properties
Number of properties	68
U.S. and Puerto Rico | The Mills
Real Estate Properties
Number of properties	14
U.S. and Puerto Rico | Community Centers
Real Estate Properties
Number of properties	3
U.S. and Puerto Rico | Other
Real Estate Properties
Number of properties	14
Japan | Premium Outlets
Real Estate Properties
Number of properties	9
South Korea | Premium Outlets
Real Estate Properties
Number of properties	3
Canada | Premium Outlets
Real Estate Properties
Number of properties	2
Mexico | Premium Outlets
Real Estate Properties
Number of properties	1
Malaysia | Premium Outlets
Real Estate Properties
Number of properties	1
Europe | Klepierre
Real Estate Properties
Joint venture ownership percentage	18.30%	28.90%
Number of countries | item	16
Europe | Premium Outlets | McArthurGlen Group
Real Estate Properties
Number of properties	5
Italy | Premium Outlets
Real Estate Properties
Number of properties	2
Austria | Premium Outlets
Real Estate Properties
Number of properties	1
Netherlands | Premium Outlets
Real Estate Properties
Number of properties	1
United Kingdom | Premium Outlets
Real Estate Properties
Number of properties	1