Leases (Maturity of Lease Liabilities) (Details) $ in Millions	Mar. 31, 2019 USD ($)
Operating leases
2019	$ 164
2020	179
2021	147
2022	108
2023	74
Thereafter	87
Total lease payments	759
Less amount representing interest	(93)
Present value of lease liabilities	666
Finance leases
2019	33
2020	39
2021	36
2022	12
2023	12
Thereafter	5
Total lease payments	137
Less amount representing interest	(18)
Present value of lease liabilities	$ 119