Commitments and Contingencies (Details 2) $ in Millions	Dec. 31, 2015 USD ($)
Other Commitments [Line Items]
2016	$ 626
2017	540
2018	454
2019	397
2020	353
2021 and Thereafter	2,172
Total	4,542
Drilling, Equipment, and Purchase Obligations
Other Commitments [Line Items]
2016	291
2017	167
2018	22
2019	16
2020	10
2021 and Thereafter	9
Total	515
Transportation and Gathering Obligations
Other Commitments [Line Items]
2016	217
2017	248
2018	314
2019	305
2020	270
2021 and Thereafter	1,816
Total	3,170
Operating Lease Obligations
Other Commitments [Line Items]
2016	42
2017	44
2018	39
2019	26
2020	26
2021 and Thereafter	168
Total	345
Capital Lease and Other Obligations
Other Commitments [Line Items]
2016	76
2017	81
2018	79
2019	50
2020	47
2021 and Thereafter	179
Total	$ 512