Real Estate Assets, Discontinued Operations and Assets Held for Sale (Table Illustration of Discontinued Operations in Income Statement) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Discontinued Operations
Payments For Second Generation Tenant Improvements Leasing Costs And Building Improvements			$ 20,112	$ 30,237
Revenues	$ 35,165	$ 42,736	81,404	84,181
Operating Expenses	(11,170)	(13,760)	(26,166)	(27,137)
Depreciation and Amortization, Discontinued Operations	(6,315)	(19,025)	(25,849)	(37,290)
Operating Income (Loss)	17,680	9,951	29,389	19,754
Disposal Group, Including Discontinued Operation, Interest Expense	(6,585)	(7,673)	(14,204)	(15,270)
Income before gain on sales	11,095	2,278	15,185	4,484
Discontinued Operation, Gain (Loss) from Disposal of Discontinued Operation, before Income Tax	1,109,091	252	1,109,091	166
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax	1,120,186	2,530	1,124,276	4,650
Discontinued Operation, Tax Effect of Discontinued Operation	(11,613)	0	(11,613)	0
Income from discontinued operations	$ 1,108,573	$ 2,530	1,112,663	4,650
Discontinued Operations [Member]
Discontinued Operations
Payments For Second Generation Tenant Improvements Leasing Costs And Building Improvements			$ 20,600	$ 54,800