Recent Accounting Pronouncements - Narrative (Details) - USD ($) $ in Millions	Jan. 01, 2019	Sep. 30, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets		$ 290	$ 0
Other current liabilities		693	567
Other long-term liabilities		87	$ 280
Present value of operating lease liabilities		$ 342
Weighted average remaining lease term, operating leases		5 years
Weighted average remaining lease term, finance leases		3 years
Weighted average discount rate, operating leases		5.50%
Weighted average discount rate, finance leases		4.80%
Operating lease, not yet commenced		$ 15
Lessee, Operating Lease, Lease Not yet Commenced, Term, Maximum		10 years
Lessee, Operating Lease, Lease Not yet Commenced, Renewal Term		4 years
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets	$ 387
Other current liabilities	103
Other long-term liabilities	(21)
Present value of operating lease liabilities	316
Effect to opening retained earnings (deficit)	$ (8)