Leases - Future Minimum Lease Payments Due Under ASC 840 Guidance (Details) $ in Millions	Dec. 31, 2018 USD ($)
Operating Leases
2019	$ 297
2020	234
2021	196
2022	154
2023	110
Thereafter	698
Total future minimum lease payments	1,689
Capital Leases
2019	92
2020	84
2021	78
2022	79
2023	30
Thereafter	70
Total future minimum lease payments	433
Less amount representing interest	95
Less amount representing executory costs	19
Present value of net minimum lease payments	319
Less current maturities of capital lease liabilities	64
Noncurrent capital lease liabilities	$ 255

Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

Reference 2: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84164817&loc=d3e45280-112737