Income Taxes:	3 Months Ended
Mar. 31, 2019
Income Tax Disclosure [Abstract]
Income Tax Disclosure [Text Block]	Income Taxes Income taxes were accrued at an estimated effective tax rate of 7% and (28)% for the three months ended March 31, 2019 and 2018, respectively. The effective tax rate for the three months ended March 31, 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 months ended March 31, 2019 included a tax benefit of $5.6 million 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 $1.8 million for the three months ended March 31, 2019, which was treated as a discrete item. The effective tax rate for the three months ended March 31, 2018 differs from the federal statutory rate of 21% principally because of the effect the mix of U.S. and foreign incomes, state income taxes, tax credits and impact of a contract settlement. The contract settlement resulted in a material tax benefit of $5.7 million, which is treated as a discrete item. The effective tax rate during the three months ended March 31, 2018 also included a material tax benefit of $3.4 million 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.

Income Taxes

Income taxes were accrued at an estimated effective tax rate of 7% and (28)% for the three months ended March 31, 2019 and 2018, respectively.

The effective tax rate for the three months ended March 31, 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 months ended March 31, 2019 included a tax benefit of $5.6 million 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 $1.8 million for the three months ended March 31, 2019, which was treated as a discrete item.

The effective tax rate for the three months ended March 31, 2018 differs from the federal statutory rate of 21% principally because of the effect the mix of U.S. and foreign incomes, state income taxes, tax credits and impact of a contract settlement. The contract settlement resulted in a material tax benefit of $5.7 million, which is treated as a discrete item. The effective tax rate during the three months ended March 31, 2018 also included a material tax benefit of $3.4 million 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.