Discontinued Operations - Effective Tax Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Provision (benefit) for income taxes	$ 6,882	$ 7,136	$ 4,589
Cole Capital [Member] | Held-for-sale of Disposed of by Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss before taxes	(5,278)	(134,774)	(225,392)
Less: Income from non-taxable entities	(9,523)	(9,008)	(8,440)
Loss attributable to taxable subsidiaries before income taxes	(14,801)	(143,782)	(233,832)
Federal provision at statutory rate (35%)	(5,180)	(50,324)	(81,841)
Impairment of goodwill	0	42,327	48,880
Nondeductible portion of transaction costs and loss recognized on classification as held for sale	8,283	0	0
Impact of change in federal tax rate	3,481	0	0
Impact of valuation allowance	6,165	0	0
State income taxes and other	1,090	(2,840)	(7,931)
Provision (benefit) for income taxes	$ 13,839	$ (10,837)	$ (40,892)