Recently Issued or Adopted Accounting Standards (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Excess tax benefits	$ 17
Reclassified financing activity in cash flow	(618)	$ (440)
Reclassified operating activity in cash flow	674	640
Accounting Standards Update 2016-09, Excess Tax Benefit Component
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassified financing activity in cash flow		(19)
Reclassified operating activity in cash flow		19
Accounting Standards Update 2016-09, Cash Flow Classifications Component
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassified financing activity in cash flow	$ 44	50
Reclassified operating activity in cash flow		$ (50)