Income Taxes:

6 Months Ended

Jun. 30, 2019

Income Tax Disclosure [Abstract]

Income Tax Disclosure [Text Block]

Income Taxes

Income taxes were accrued at an estimated effective tax rate of 17% and 12% for the three and six months ended June 30, 2019, respectively, as compared to (5)% and (8)% for the three and six months ended June 30, 2018, respectively.

The effective tax rate for the three and six months ended June 30, 2019 differs from the federal statutory rate of 21% principally because of the effect of the mix of U.S. and foreign incomes, state income taxes, global intangible low-taxed income (GILTI) and tax credits. It is also affected by discrete items that may occur in any given year but are not consistent from year to year. The effective tax rate during the three and six months ended June 30, 2019 included a tax benefit of $1.8 million and $7.4 million, respectively, related to the excess tax benefits recognized on stock option exercises and the vesting of restricted stock units during the period, which is treated as a discrete item and excluded from determining our annual estimated effective tax rate. In addition, a revaluation of the contingent consideration resulted in a tax provision of $9.5 million and $11.3 million for the three and six months ended June 30, 2019, respectively, which is treated as a discrete item.

The effective tax rate for the three and six months ended June 30, 2018 differs from the federal statutory rate of 21% principally because of the effect of the mix of U.S. and foreign incomes, state income taxes and tax credits. The effective tax rate during the three and six months ended June 30, 2018 included a material tax benefit of $7.8 million and $11.2 million, respectively, related to the excess tax benefits recognized on stock option exercises and the vesting of restricted stock units during the period, which is treated as a discrete item and excluded from determining our annual estimated effective tax rate. The effective tax rate for the six months ended June 30, 2018 was also impacted by a contract settlement. The contract settlement resulted in a material tax benefit of $5.7 million, which is treated as a discrete item.