CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) shares in Millions, $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 254	$ 250
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	600	600
Common stock, shares issued	216	215
Treasury stock, shares	73	71