Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Millions, $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Balance Sheet Parentheticals [Abstract]
Allowance for receivables	$ 60	$ 60
Common Class A [Member]
Class of Stock [Line Items]
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	375	375
Common stock, shares issued	38	38
Common Class B [Member]
Class of Stock [Line Items]
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	5,000	5,000
Common stock, shares issued	831	829
Treasury stock, at cost, Class B shares	462	455