Other Assets and Other Liabilities (Schedule of Other Assets) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Deferred Expenses and Other Assets, Net
Intangible assets, net	$ 162,014		$ 162,014		$ 27,124
Other receivables	47,355		47,355		56,369
Other assets	29,952		29,952		23,081
Restricted cash	27,399	$ 23,380	27,399	$ 23,380	20,045	$ 25,883
Leasing costs, net	7,141		7,141		9,050
Corporate furniture, fixtures and equipment, net	4,362		4,362		4,652
Deferred financing fees, net	1,167		1,167		1,409
Deferred expenses and other assets, net	279,390		279,390		141,730
Intangible assets, accumulated amortization	30,900		30,900		34,900
Amortization of above market lease	400	800	800	1,600
Accumulated amortization on leasing costs	3,900		3,900		4,700
Accumulated depreciation on corporate furniture, fixtures and equipment	11,200		11,200		10,500
Depreciation and Amortization
Deferred Expenses and Other Assets, Net
Amortization of intangible assets	400	$ 700	700	$ 1,200
Operating Properties
Deferred Expenses and Other Assets, Net
Other receivables	26,500		26,500		$ 26,000
Net lease venture
Deferred Expenses and Other Assets, Net
Intangible assets, net	$ 135,300		$ 135,300