Leases - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Leases [Abstract]
Rental expense for operating leases	$ 113
Rental expense for operating leases		$ 124	$ 120
Rental expense related to capitalized operating leases	69
Rental expense related to short-term operating leases and variable lease payments	44
Operating lease right-of-use asset	206
Current portion of lease liability for operating leases	51
Long-term portion of lease liability for operating leases	$ 128
Weighted average remaining lease term of operating leases included in lease liability	4 years 7 months 6 days
Weighted average discount rate of operating leases included in lease liability	2.59%
Cash paid related to maturities of operating lease liabilities	$ 70
Operating lease right-of-use assets obtained in exchange for operating lease liabilities	$ 50