Leases - Right-of-use Assets and Liability (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
ROU Assets
Operating Leases	$ 273	$ 0
Finance Leases	179
Total ROU Assets	452
Current Liabilities
Operating Leases	86
Finance Leases	41	41
Noncurrent Liabilities
Operating Leases	194	$ 0
Finance Leases	174
Total Lease Liabilities	495
Accumulated amortization	449
Office Space
ROU Assets
Operating Leases	107
Finance Leases	96
Compressors
ROU Assets
Operating Leases	87
Drilling Rigs
ROU Assets
Operating Leases	$ 40