Consolidated Balance Sheets (Unaudited) (Parentheticals) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Current Assets:
Allowance for uncollectible accounts	$ 11	$ 15
Allowance for obsolescence	119	110
Property and equipment additions:
Accumulated depreciation and amortization	13,336	12,456
Other Assets:
Accumulated amortization of identifiable intangible assets	$ 837	$ 828
Stockholders' Equity:
Common stock, par value per share (in usd per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized	1,500,000,000	1,500,000,000
Common stock, shares issued	731,451,949	744,886,938
Treasury stock, at cost, shares	7,421,731	14,149,229