Leases - Cash Flow Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)
Cash Flow, Lessee [Abstract]
Operating Cash Flows, Operating Leases	$ 15
Operating Cash Flows, Finance Leases	3
Financing Cash Flows, Finance Leases	10
Investing Cash Flows, Operating Leases	9
ROU Assets Obtained in Exchange for Lease Liability, Operating	34
ROU Assets Obtained in Exchange for Lease Liability, Finance	$ 2