Leases - Depreciation Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
General and Administrative Expense
Lessor, Lease, Description [Line Items]
Depreciation expense related to corporate assets	$ 2	$ 4	$ 1
Other Assets
Lessor, Lease, Description [Line Items]
Accumulated depreciation related to corporate assets	$ 4	$ 2