. as a result of the reduction of the federal corporate income tax rate , the company has revalued its net deferred tax liability , excluding after tax credits , as of december 31 , 2017 . based on this revaluation and other impacts of the 2017 tax act , the company has recognized a net tax benefit of $ 2.6 billion , which was recorded as a reduction to income tax expense for the year ended december 31 , 2017