Commitments and Contingencies Purchase Obligations and Operating Lease Commitment Tables (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Consolidated operating leases future minimum payments due
2019	$ 196
2020	175
2021	152
2022	134
2023	85
Thereafter	235
Future minimum payments under operating leases	977
Rent expense	168	$ 155	$ 136
Energy Segment
Unconditional purchase obligations
2019	129
2020	89
2021	78
2022	76
2023	75
Thereafter	444
Minimum required payments for unconditional purchase obligations	891
Amounts purchased under supply agreements	$ 214	$ 209	$ 151