Debt - Deferred Financing Costs, Net (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Debt Instrument [Line Items]
Financing costs	$ 25,312		$ 25,312		$ 24,446
Less: accumulated amortization	(9,006)		(9,006)		(7,039)
Total deferred financing costs, net	16,306		16,306		17,407
Amortization of deferred financing costs	1,100	$ 1,000	3,100	$ 3,600
Unsecured term loan facility | Unsecured Revolving Credit Facility
Debt Instrument [Line Items]
Net deferred financing costs	$ 6,800		$ 6,800		$ 8,300