Consolidated Balance Sheets (Unaudited) (Parentheticals) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Current Assets:
Allowance for uncollectible accounts	$ 11	$ 9
Allowance for obsolescence	114	114
Property and equipment additions:
Accumulated depreciation and amortization	11,314	10,871
Other Assets:
Accumulated amortization of identifiable intangible assets	$ 815	$ 811
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	785,605,157	799,850,675
Treasury stock, at cost, shares	14,023,717	21,066,684