Income taxes	9 Months Ended
Sep. 30, 2012
Income Tax Disclosure [Abstract]
Income taxes	Income taxes Federal income taxes for the interim periods presented have been included in the accompanying financial statements on the basis of an estimated annual effective tax rate. The rate is based on current tax law and for 2012 does not assume reinstatement of the federal research tax credit, which expired at the end of 2011. As of September 30, 2012, the estimated annual effective tax rate for 2012 is about 22 percent, which differs from the 35 percent statutory corporate tax rate due to the impact of non-U.S. effective tax rates. The third-quarter 2012 tax provision includes a $90 million discrete tax benefit that was primarily the result of additional U.S. tax benefits for manufacturing related to years 2007 through 2011, and a $67 million benefit from the cumulative effect of our lowering the estimated effective tax rate for 2012. The lower tax rate estimate was primarily due to a revised estimate of the impact of non-U.S. effective tax rates. With respect to the benefits for manufacturing, we may seek additional deductions for years prior to 2007 and, as a result, may recognize an additional discrete item in the fourth quarter.

Income taxes

9 Months Ended

Sep. 30, 2012

Federal income taxes for the interim periods presented have been included in the accompanying financial statements on the basis of an estimated annual effective tax rate. The rate is based on current tax law and for 2012 does not assume reinstatement of the federal research tax credit, which expired at the end of 2011. As of September 30, 2012, the estimated annual effective tax rate for 2012 is about 22 percent, which differs from the 35 percent statutory corporate tax rate due to the impact of non-U.S. effective tax rates. The third-quarter 2012 tax provision includes a $90 million discrete tax benefit that was primarily the result of additional U.S. tax benefits for manufacturing related to years 2007 through 2011, and a $67 million benefit from the cumulative effect of our lowering the estimated effective tax rate for 2012. The lower tax rate estimate was primarily due to a revised estimate of the impact of non-U.S. effective tax rates. With respect to the benefits for manufacturing, we may seek additional deductions for years prior to 2007 and, as a result, may recognize an additional discrete item in the fourth quarter.