Commitments and Contingencies - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) property	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Loss Contingencies [Line Items]
Third party debt collateralized by facilities, debt amount	$ 83
Third party debt collateralized by facilities, asset carrying amount	356
Rental Expense
Rental expense attributable to continuing operations	$ 10	$ 10	$ 10
Maximum remaining term of ground leases excluding extension options	99 years
Indemnification Agreement
Loss Contingencies [Line Items]
Number of properties may be contributed in the agreement | property	35