Lease Obligations - Lessee - Undiscounted Cash Flows (Details) $ in Millions	Jun. 30, 2019 USD ($)
Operating Leases
Remainder of 2019	$ 49
2020	89
2021	76
2022	69
2023	61
2024	52
Thereafter	232
Total undiscounted cash flows	628
Less: Difference between undiscounted cash flows and discounted cash flows	(93)
Operating lease liabilities	535
Finance Leases
Remainder of 2019	3
2020	5
2021	4
2022	3
2023	0
2024	0
Thereafter	2
Total undiscounted cash flows	17
Less: Difference between undiscounted cash flows and discounted cash flows	(2)
Finance lease liabilities	15
Total
Remainder of 2019	52
2020	94
2021	80
2022	72
2023	61
2024	52
Thereafter	234
Total undiscounted cash flows	645
Less: Difference between undiscounted cash flows and discounted cash flows	(95)
Total lease liabilities	$ 550