Lease Obligations - Lessee - Undiscounted Cash Flows (Details) $ in Millions	Sep. 30, 2019 USD ($)
Operating Leases
Remainder of 2019	$ 25
2020	88
2021	77
2022	72
2023	63
2024	55
Thereafter	258
Total undiscounted cash flows	638
Less: Difference between undiscounted cash flows and discounted cash flows	(95)
Operating lease liabilities	543
Finance Leases
Remainder of 2019	2
2020	6
2021	5
2022	4
2023	1
2024	1
Thereafter	14
Total undiscounted cash flows	33
Less: Difference between undiscounted cash flows and discounted cash flows	(7)
Finance lease liabilities	26
Total
Remainder of 2019	27
2020	94
2021	82
2022	76
2023	64
2024	56
Thereafter	272
Total undiscounted cash flows	671
Less: Difference between undiscounted cash flows and discounted cash flows	102
Total lease liabilities	$ 569