Consolidated Statements of Financial Position (Unaudited) (Parenthetical) (Parentheticals) (USD $) In Millions, except Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Allowance for doubtful accounts	$ 59	$ 62
Common stock, par value	$ 0	$ 0
Common stock, shares authorized	400,000,000	400,000,000
Common stock, shares issued	173,950,853	172,351,680
Common stock, shares outstanding	173,950,853	172,351,680