Mergers, Acquisitions and Dispositions Proforma Impact of Merger (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	[3]	Dec. 31, 2016		Dec. 31, 2015
Business Acquisition, Pro Forma Revenue			$ 32,342	[1]	$ 33,823	[2]
Business Acquisition, Pro Forma Net Income (Loss)			$ 1,562	[1]	$ 2,618	[2]
Business Acquisition, Pro Forma Earnings Per Share, Basic			$ 1.69	[1]	$ 2.85	[2]
Business Acquisition, Pro Forma Earnings Per Share, Diluted			$ 1.69	[1]	$ 2.84	[2]
Noncash Merger Related Costs	$ 0		$ 558	[4],[5]
Consolidation, Eliminations [Member]
Business Acquisition, Pro Forma Revenue			171		$ 559
Noncash Merger Related Costs			$ 680		$ 92

[1] The amounts above exclude non-recurring costs directly related to the merger of $680 million and intercompany revenue of $171 million for the year ended December 31, 2016

[2] The amounts above exclude non-recurring costs directly related to the merger of $92 million and intercompany revenue of $559 million for the year ended December 31, 2015

[3] See Note 4 - Mergers, Acquisitions and Dispositions for more information.

[4] 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.

[5] See Note 4 - Mergers, Acquisitions and Dispositions for more information.