Property: (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended				1 Months Ended	12 Months Ended	1 Months Ended	12 Months Ended		0 Months Ended	12 Months Ended	0 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Fiesta Mall	Feb. 28, 2011 Desert Sky Mall	Dec. 31, 2011 Desert Sky Mall	Jun. 30, 2011 Superstition Springs Land	Dec. 31, 2011 Superstition Springs Land	Jun. 03, 2011 Superstition Springs Land	Oct. 03, 2012 FlatIron Crossing	Dec. 31, 2012 FlatIron Crossing	Oct. 26, 2012 Arrowhead Towne Center	Dec. 31, 2012 Arrowhead Towne Center
Purchase of interest in property
Remeasurement gain on acquisition of additional interest	$ 115,729				$ 1,868	$ 1,868	$ 1,734	$ 1,734		$ 84,227	$ 84,227	$ 115,729	$ 115,729
Ownership percentage purchased					50.00%	50.00%	50.00%		50.00%	75.00%	75.00%	33.30%	33.30%
Write off of development cost	19,204
Impairment charge		25,216		24,555
Loss on sale of assets	$ 390	$ 423	$ 497