Discontinued Operations: (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended			1 Months Ended					12 Months Ended		1 Months Ended		1 Months Ended			1 Months Ended			1 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	May 31, 2012 Mervyn's	Nov. 30, 2011 Mervyn's	Oct. 31, 2011 Mervyn's	Mar. 31, 2011 Mervyn's	Jul. 31, 2009 Mervyn's item	Dec. 31, 2011 Shoppingtown Mall	Jun. 29, 2011 Shoppingtown Mall	Apr. 30, 2012 Valley View Mall	Mar. 31, 2012 Valley View Mall	Apr. 30, 2012 The Borgata sqft	May 31, 2012 Hilton Village.	May 17, 2012 Hilton Village. sqft	May 31, 2012 Prescott Gateway sqft	Jun. 30, 2012 Carmel Plaza	Jun. 28, 2012 Carmel Plaza sqft	Jun. 30, 2011 GGP Exchange store	Jun. 30, 2011 GGP Exchange Mervyn's entity
Discontinued Operations:
Impairment charge										$ 35,729		$ 54,306
Number of locations sold								5
Proceeds from sale				20,750	2,300	8,061	3,732						9,150	24,820			52,000
Gain (loss) from sale	74,833	(58,230)	(23)	(407)	(200)	3,783	(1,913)						(1,275)	3,127			7,844
Property square footage													94,000		80,000	584,000		112,000
Long-lived assets written off to fair value										38,968		33,450
Gain (loss) on extinguishment of debt		(10,588)	3,661						(3,929)		104,023					16,296
Number of anchor locations exchanged																			6	5
Revenues from discontinued operations	10,601	39,931	47,002
Gain (loss) income from discontinued operations	$ 69,365	$ (74,871)	$ (10,350)