Assets and Liabilities Measured at Fair Value (Nonrecurring) (Details) - USD ($) $ in Thousands	3 Months Ended						10 Months Ended	12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2014	Dec. 31, 2013	Apr. 05, 2013	Oct. 22, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Assets and liabilities measured at fair value
Impairment charge								$ 11,540	$ 9,371	$ 363
Fair Value, Measurements, Nonrecurring [Member]
Assets and liabilities measured at fair value
Impairment charge								12,300
Fair Value, Measurements, Nonrecurring [Member] | Chase Park Plaza - The Private Residences [Member]
Assets and liabilities measured at fair value
Condominium inventory impairment charges					$ 300
Impairment of intangible assets, related to real estate inventory					$ 200
Fair Value, Measurements, Nonrecurring [Member] | Becket House | Discontinued operations
Assets and liabilities measured at fair value
Condominium inventory impairment charges						$ 300
Fair Value, Measurements, Nonrecurring [Member] | 4950 S Bowen Road | Continuing operations
Assets and liabilities measured at fair value
Condominium inventory impairment charges							$ 100
Chase Private Residences [Member]
Assets and liabilities measured at fair value
Impairment charge	$ 100		$ 600					700
Northborough Tower [Member]
Assets and liabilities measured at fair value
Impairment charge		$ 2,100						2,100	9,400
Northpoint Central
Assets and liabilities measured at fair value
Impairment charge		2,700						2,700
Buildings and Improvements | Northborough Tower [Member]
Assets and liabilities measured at fair value
Impairment charge				$ 9,400
Buildings and Improvements | Fair Value, Measurements, Nonrecurring [Member]
Assets and liabilities measured at fair value
Assets, Fair Value Disclosure, Nonrecurring				19,397					19,397
Land [Member] | Frisco Square [Member]
Assets and liabilities measured at fair value
Impairment charge		$ 6,800						6,800
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets and liabilities measured at fair value
Assets, Fair Value Disclosure, Nonrecurring	2,201							2,201
Fair Value, Inputs, Level 3 [Member] | Buildings and Improvements | Fair Value, Measurements, Nonrecurring [Member]
Assets and liabilities measured at fair value
Assets, Fair Value Disclosure, Nonrecurring	29,500			19,397				29,500	19,397
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets and liabilities measured at fair value
Assets, Fair Value Disclosure, Nonrecurring	0							0
Fair Value, Inputs, Level 1 [Member] | Buildings and Improvements | Fair Value, Measurements, Nonrecurring [Member]
Assets and liabilities measured at fair value
Assets, Fair Value Disclosure, Nonrecurring				0					0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets and liabilities measured at fair value
Assets, Fair Value Disclosure, Nonrecurring	0							0
Fair Value, Inputs, Level 2 [Member] | Buildings and Improvements | Fair Value, Measurements, Nonrecurring [Member]
Assets and liabilities measured at fair value
Assets, Fair Value Disclosure, Nonrecurring				0					0
Land and Land Improvements [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets and liabilities measured at fair value
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	(6,762)							(6,762)
Land and Land Improvements [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets and liabilities measured at fair value
Assets, Fair Value Disclosure, Nonrecurring	19,606							19,606
Changes Measurement [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets and liabilities measured at fair value
Assets, Fair Value Disclosure, Nonrecurring	(761)							(761)
Changes Measurement [Member] | Buildings and Improvements | Fair Value, Measurements, Nonrecurring [Member]
Assets and liabilities measured at fair value
Assets, Fair Value Disclosure, Nonrecurring	(4,778)			(9,371)				(4,778)	(9,371)
Income Approach Valuation Technique [Member] | Investment Building and Building Improvements [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets and liabilities measured at fair value
Assets, Fair Value Disclosure, Nonrecurring	29,500			$ 19,397				29,500	$ 19,397
Income Approach Valuation Technique [Member] | Land and Land Improvements [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets and liabilities measured at fair value
Assets, Fair Value Disclosure, Nonrecurring	19,606							19,606
Market Approach Valuation Technique [Member] | Inventory, Real Estate [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets and liabilities measured at fair value
Assets, Fair Value Disclosure, Nonrecurring	$ 2,201							$ 2,201