Rent and Tenant Receivables and Other Assets, Net (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Accounts receivable, net	$ 42,274		$ 36,921
Straight-line rent receivable, net	241,733		230,529
Deferred costs, net	3,213		5,746
Prepaid expenses	9,392		6,493
Leasehold improvements, property and equipment, net	11,230		12,089
Restricted escrow deposits	4,175		4,995
Income tax receivable	2,310		3,213
Investment in Cole REITs	7,844		3,264
Subordinate Promissory Note outstanding principal balance	3,200		0
Other amounts due from Cole REITs	4,957		0
Other assets, net	5,294		5,003
Total	335,622		308,253
Interest receivable reserves	2,300		1,800
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Amortization expense	300	$ 300
Accumulated amortization	5,000		4,700
Property and Equipment [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense	500	400
Line of Credit [Member]
Property, Plant and Equipment [Line Items]
Amortization expense	2,600	$ 2,600
Accumulated amortization for deferred costs	42,900		40,300
Accounts Receivable [Member]
Property, Plant and Equipment [Line Items]
Allowance for doubtful accounts	5,500		6,300
Rent Receivables [Member]
Property, Plant and Equipment [Line Items]
Allowance for doubtful accounts	$ 1,300		$ 2,000