Rosetta Merger - Narrative (Details) $ / shares in Units, a in Thousands, shares in Millions, $ in Millions			3 Months Ended				9 Months Ended				12 Months Ended
		Jul. 20, 2015 USD ($) a business $ / shares shares	Sep. 30, 2016 USD ($)		Sep. 30, 2015 USD ($)		Sep. 30, 2016 USD ($)		Sep. 30, 2015 USD ($)	[1]	Dec. 31, 2015 USD ($)
Business Acquisition [Line Items]
Other Noncash Income			$ 0	[1]	$ 0	[1]	$ 25		$ 0
Shares exchange in acquisition | shares		41
Rosetta Merger Expenses			0		$ 71		0	[1]	$ 73
Pro forma revenue			119				333
Pro forma pre-tax net income			$ 4				$ 17
Rosetta Resources, Inc [Member]
Business Acquisition [Line Items]
Shares exchange in acquisition | shares		41
Number of onshore plays added in acquisition | business		2
Merger related costs including noncash share-based compensation expense											$ 81
Rosetta Merger Expenses											66
Merger related costs related to noncash share-based compensation											$ 15
Share price | $ / shares		$ 36.97
Eagle Ford Shale [Member] | Rosetta Resources, Inc [Member]
Business Acquisition [Line Items]
Liquid rich asset based acquired | a		50
Permian [Member] | Rosetta Resources, Inc [Member]
Business Acquisition [Line Items]
Liquid rich asset based acquired | a		54
Delaware Basin [Member] | Rosetta Resources, Inc [Member]
Business Acquisition [Line Items]
Liquid rich asset based acquired | a		45
Midland Basin [Member] | Rosetta Resources, Inc [Member]
Business Acquisition [Line Items]
Long-term Debt, Fair Value	[2]	$ 2,000
Liquid rich asset based acquired | a		9
Common Stock | Rosetta Resources, Inc [Member]
Business Acquisition [Line Items]
Exchange ratio of common shares for acquired company		0.542

[1] Amount relates to an adjustment recorded to the purchase price allocation related to the Rosetta Merger. See Note 5. Rosetta Merger.

[2] (1) Net of unamortized discount, premium and debt issuance costs and excludes capital lease and other obligations.