Leases - Additional Information Related to Leases (Details) $ in Millions	6 Months Ended
	Jun. 30, 2019 USD ($)
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 166
Operating cash flows from finance leases	12
Financing cash flows from finance leases	29
Right-of-use assets obtained in exchange for lease liabilities:
Operating leases	95
Finance leases	$ 4
Weighted-average remaining lease term:
Operating leases	10 years 9 months 18 days
Finance leases	5 years 4 months 24 days
Weighted-average discount rate:
Operating leases	4.00%
Finance leases	9.00%