Summary of Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended		8 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2018	Sep. 30, 2017
Deferred Revenue Arrangement [Line Items]
Total return on stockholders' capital, exceeding benchmark	6.00%		6.00%	6.00%
Service agreement, cost of services	$ 4,100		$ 12,200
Other income, net	(1,016)	$ 1,131		$ 7,635	$ 4,253
Cole Capital [Member] | Held-for-sale of Disposed of by Sale [Member]
Deferred Revenue Arrangement [Line Items]
Contingent consideration, payment period				6 years
Contingent consideration, maximum consideration receivable	80,000		80,000	$ 80,000
Service Agreement [Member]
Deferred Revenue Arrangement [Line Items]
Other income, net	$ 4,000		$ 12,100