Discontinued Operations - Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss from discontinued operations	$ (30,613)	$ 4,005	$ 4,636	$ 2,855	$ (128,926)	$ 1,381	$ 2,987	$ 621	$ (19,117)	$ (123,937)	$ (184,500)
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]
Offering-related fees and reimbursements									16,096	36,526	24,412
Transaction service fees and reimbursements									13,929	12,533	25,256
Management fees and reimbursements									76,214	68,686	58,793
Total revenues									106,239	117,745	108,461
Cole Capital reallowed fees and commissions									9,879	23,174	16,195
Transaction costs									3,802	0	0
General and administrative									63,783	82,558	79,602
Amortization of intangible assets									14,490	26,148	25,884
Goodwill and intangible asset impairments									0	120,931	213,339
Total operating expenses									91,954	252,811	335,020
Operating income (loss)									14,285	(135,066)	(226,559)
Other income (expense), net									464	292	1,167
Loss recognized on classification as held for sale									(20,027)	0	0
Loss before taxes									(5,278)	(134,774)	(225,392)
(Provision for) benefit from income taxes									(13,839)	10,837	40,892
Loss from discontinued operations									$ (19,117)	$ (123,937)	$ (184,500)