Commitments and Contingencies - Environmental Matters (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Jun. 30, 2017
Loss Contingencies [Line Items]
Accrued expenses and other current liabilities			$ 8	$ 12
Deferred credits and other liabilities			28	28
Environmental remediation accrual, discounted basis			$ 36	$ 40
Weighted average discount rate			1.30%
Expected payments of environmental remediation costs, 2020			$ 7
Expected payments of environmental remediation costs, 2021			4
Expected payments of environmental remediation costs, 2022			3
Expected payments of environmental remediation costs, 2023			2
Expected payments of environmental remediation costs, 2024			2
Expected payments of environmental remediation costs, thereafter			15
Expenditures for property, plant and equipment 2021			15
Expenditures for property, plant and equipment 2022			17
Estimated liability			44		$ 132
Payments for settlement			79
Change in reserve		$ 9
Forecast
Loss Contingencies [Line Items]
Payments for settlement	$ 30
Accrued expenses and other current liabilities
Loss Contingencies [Line Items]
Estimated liability			30
Deferred credits and other liabilities
Loss Contingencies [Line Items]
Estimated liability			$ 14