Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Current Assets:
Allowance for uncollectible accounts	$ 10	$ 11
Allowance for obsolescence	120	127
Property and equipment additions:
Accumulated depreciation and amortization	10,140	9,340
Other Assets:
Accumulated amortization	$ 802	$ 793
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	816,405,334	845,048,310
Treasury stock, at cost, shares	21,007,002	19,790,077