CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) shares in Thousands, $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Accounts receivable, allowance	$ 149	$ 152
Preferred stock-non-redeemable, par value (in dollars per share)	$ 25.00	$ 25.00
Preferred stock-non-redeemable, authorized shares (shares)	2,000	2,000
Preferred stock-non-redeemable, issued shares (shares)	7	7
Preferred stock-non-redeemable, outstanding shares (shares)	7	7
Common stock, par value (in dollars per share)	$ 1.00	$ 1.00
Common stock, authorized shares (shares)	1,600,000	1,600,000
Common stock, issued shares (shares)	546,164	543,800
Common stock, outstanding shares (shares)	546,164	543,800
Customer relationships
Finite-lived intangible assets, accumulated amortization	$ 5,878	$ 5,648
Other intangible assets
Finite-lived intangible assets, accumulated amortization	$ 1,879	$ 1,798