Mergers, Acquisitions, and Dispositions ProForma Impact of Merger (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended			12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016		Dec. 31, 2016
Business Acquisition, Pro Forma Revenue		$ 8,556	[1]	$ 32,342	[2]
Business Acquisition, Pro Forma Net Income (Loss)		$ 577	[1]	$ 1,562	[2]
Business Acquisition, Pro Forma Earnings Per Share, Basic		$ 0.63	[1]	$ 1.69	[2]
Business Acquisition, Pro Forma Earnings Per Share, Diluted		$ 0.62	[1]	$ 1.69	[2]
Noncash Merger Related Costs		$ 503
Consolidation, Eliminations [Member]
BusinessCombinationProformaIntercompanyRevenue		170
Business Acquisition, Pro Forma Revenue				$ 171
Noncash Merger Related Costs	$ 680	$ 639

[1] The amounts above include adjustments for non-recurring costs directly related to the merger of $639 million and intercompany revenue of $170 million for the three months ended March 31, 2016.

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