Income Taxes	3 Months Ended
Mar. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The effective tax rates were 23.3 percent and 14.5 percent for the three months ended March 31, 2019 and 2018, respectively. The higher effective tax rate is primarily due to the non-deductibility of accelerated vesting of Loxo employee equity awards as part of the closing of the acquisition of Loxo, as well as tax expenses associated with the suspension of promotion of Lartruvo. In 2017, the U.S. enacted the Tax Cuts and Jobs Act (2017 Tax Act), which significantly revised U.S. tax law. Guidance related to the 2017 Tax Act, including Notices, Proposed Regulations, and Final Regulations, has been issued, and we expect additional guidance will be issued in 2019. This additional guidance could materially impact our assumptions and estimates used to record our U.S. federal and state income tax expense resulting from the 2017 Tax Act. The U.S. examination of tax years 2013-2015 began in 2016, and we believe it is reasonably possible that this examination could reach resolution within the next 12 months for the tax years 2013-2014 and certain matters under examination for tax year 2015, for which the examination remains ongoing. As a result, we currently estimate that gross uncertain tax positions may be reduced by approximately $450 million within the next 12 months. Additionally, we anticipate up to $150 million of cash payments will be due upon resolution.

Income Taxes

The effective tax rates were 23.3 percent and 14.5 percent for the three months ended March 31, 2019 and 2018, respectively. The higher effective tax rate is primarily due to the non-deductibility of accelerated vesting of Loxo employee equity awards as part of the closing of the acquisition of Loxo, as well as tax expenses associated with the suspension of promotion of Lartruvo.

In 2017, the U.S. enacted the Tax Cuts and Jobs Act (2017 Tax Act), which significantly revised U.S. tax law. Guidance related to the 2017 Tax Act, including Notices, Proposed Regulations, and Final Regulations, has been issued, and we expect additional guidance will be issued in 2019. This additional guidance could materially impact our assumptions and estimates used to record our U.S. federal and state income tax expense resulting from the 2017 Tax Act.

The U.S. examination of tax years 2013-2015 began in 2016, and we believe it is reasonably possible that this examination could reach resolution within the next 12 months for the tax years 2013-2014 and certain matters under examination for tax year 2015, for which the examination remains ongoing. As a result, we currently estimate that gross uncertain tax positions may be reduced by approximately $450 million within the next 12 months. Additionally, we anticipate up to $150 million of cash payments will be due upon resolution.