Discontinued Operations and Gain (Loss) on Disposition of Rental Properties (Details 3) (USD $)	11 Months Ended	12 Months Ended
	Dec. 31, 2013	Jan. 31, 2013	Jan. 31, 2012
Gain Loss on Disposition of Rental Properties
Gain (loss) on disposition of rental properties	$ 41,831,000	$ 100,900,000	$ 133,554,000
Millender Center [Member]
Gain Loss on Disposition of Rental Properties
Gain (loss) on disposition of rental properties	21,660,000	0	0
Emerald Palms [Member]
Gain Loss on Disposition of Rental Properties
Gain (loss) on disposition of rental properties	0	45,845,000	0
Southfield [Member]
Gain Loss on Disposition of Rental Properties
Gain (loss) on disposition of rental properties	0	13,445,000	0
Sheraton Station Square [Member]
Gain Loss on Disposition of Rental Properties
Gain (loss) on disposition of rental properties	18,096,000	0	0
Charleston Marriott [Member]
Gain Loss on Disposition of Rental Properties
Gain (loss) on disposition of rental properties	0	0	9,957,000
Ritz Carlton [Member]
Gain Loss on Disposition of Rental Properties
Gain (loss) on disposition of rental properties	0	0	2,431,000
Higbee Building [Member]
Gain Loss on Disposition of Rental Properties
Gain (loss) on disposition of rental properties	2,922,000	0	0
Colorado Studios [Member]
Gain Loss on Disposition of Rental Properties
Gain (loss) on disposition of rental properties	1,239,000	0	0
Fairmont Plaza [Member]
Gain Loss on Disposition of Rental Properties
Gain (loss) on disposition of rental properties	0	26,877,000	0
Waterfront Station - East 4th and West 4th Buildings [Member]
Gain Loss on Disposition of Rental Properties
Gain (loss) on disposition of rental properties	0	0	111,738,000
250 Huron [Member]
Gain Loss on Disposition of Rental Properties
Gain (loss) on disposition of rental properties	0	0	9,428,000
Orchard Town Center [Member]
Gain Loss on Disposition of Rental Properties
Gain (loss) on disposition of rental properties	(2,157,000)	0	0
Triple net lease properties [Member]
Gain Loss on Disposition of Rental Properties
Gain (loss) on disposition of rental properties	(132,000)	6,568,000	0
Quebec Square [Member]
Gain Loss on Disposition of Rental Properties
Gain (loss) on disposition of rental properties	0	8,879,000	0
Other [Member]
Gain Loss on Disposition of Rental Properties
Gain (loss) on disposition of rental properties	$ 203,000	$ (714,000)	$ 0