Rent and Tenant Receivables and Other Assets, Net (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Accounts receivable, net	$ 36,921,000	$ 49,114,000
Straight-line rent receivable, net	230,529,000	201,585,000
Deferred costs, net	5,746,000	16,154,000
Prepaid expenses	6,493,000	6,452,000
Leasehold improvements, property and equipment, net	12,089,000	14,702,000
Restricted escrow deposits	4,995,000	5,741,000
Income tax receivable	3,213,000	18,045,000
Interest rate swap assets, at fair value	627,000	199,000
Other assets, net	4,376,000	2,313,000
Total	304,989,000	314,305,000
Allowance for doubtful accounts	6,900,000	6,000,000
Interest receivable reserves	1,800,000	1,600,000
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Amortization expense	1,200,000	2,300,000	$ 2,200,000
Write-Off of Leasehold		1,000,000
Accumulated amortization	4,700,000	3,500,000
Property and Equipment [Member]
Property, Plant and Equipment [Line Items]
Write-Off of Leasehold	600,000
Depreciation expense	1,800,000	3,400,000	2,100,000
Write-off of property, plant and equipment		1,200,000
Line of Credit [Member]
Property, Plant and Equipment [Line Items]
Amortization expense	10,400,000	10,400,000	$ 10,700,000
Accumulated amortization for deferred costs	40,300,000	29,800,000
Accounts Receivable [Member]
Property, Plant and Equipment [Line Items]
Allowance for doubtful accounts	6,300,000	6,000,000
Rent Receivables [Member]
Property, Plant and Equipment [Line Items]
Allowance for doubtful accounts	$ 2,000,000	$ 0