Mergers, Acquisitions, and Dispositions ProForma Impact of Merger (Details) - USD ($) $ / shares in Thousands, $ in Millions		3 Months Ended		6 Months Ended		12 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Business Acquisition, Pro Forma Revenue		$ 6,910	$ 7,522	$ 15,466	$ 17,584	$ 33,823
Business Acquisition, Pro Forma Net Income (Loss)		$ 268	$ 623	$ 845	$ 1,423	$ 2,618
Business Acquisition, Pro Forma Earnings Per Share, Basic		$ 0	$ 0	$ 0	$ 0	$ 0
Business Acquisition, Pro Forma Earnings Per Share, Diluted		$ 0	$ 0	$ 0	$ 0	$ 0
Noncash Merger Related Costs	[1],[2]			$ 503
Consolidation, Eliminations [Member]
Business Acquisition, Pro Forma Revenue	[3]		$ 111	170	$ 233	$ 559
Noncash Merger Related Costs	[3]	$ 1	$ (82)	$ 641	$ 35	$ 92

[1] (e)Excludes $5 million of forgiveness of Accounts receivable related to merger commitments recorded in connection with the PHI Merger, the balance is included within Provision for uncollectible accounts.

[2] See Note 4 — Mergers, Acquisitions and Dispositions for additional information related to the merger with PHI.

[3] (a)The amounts above include adjustments for non-recurring costs directly related to the merger of $1 million and $641 million for the three and six months ended June 30, 2016, respectively, and intercompany revenue of $170 million for the six months ended June 30, 2016.