Acquisitions and Divestitures - Liabilities Assumed From Acquisition of Businesses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Combinations [Abstract]
Fair value of assets acquired	$ 253	$ 2,576	$ 67
Cash paid (net of cash acquired)	211	2,401	52
Liabilities assumed	$ 42	$ 175	$ 15