Income Taxes:	6 Months Ended
Jun. 30, 2018
Income Tax Disclosure [Abstract]
Income Tax Disclosure [Text Block]	Income Taxes On December 22, 2017, the Tax Cuts and Jobs Act (the “Tax Act”) was enacted into legislation, which includes a broad range of provisions affecting businesses. The Tax Act significantly revises how companies compute their U.S. corporate tax liability by, among other provisions, reducing the corporate tax rate from 35% to 21% for tax years beginning after December 31, 2017. Our accounting for the Tax Act is incomplete. As noted at year-end, however, we were able to reasonably estimate certain effects and, therefore, recorded provisional adjustments associated with the toll charge on undistributed foreign earnings and profits and revaluation of deferred taxes. We have not made any additional measurement-period adjustments related to these items during the quarter. However, we are continuing to gather additional information to complete our accounting for these items and expect to complete our accounting within the prescribed measurement period. Income taxes were accrued at an estimated effective tax rate of (8)% and (182)% for the six months ended June 30, 2018 and 2017, respectively. Those rates differ from that computed at the federal statutory rate of 21% for the six months ended June 30, 2018 and the federal statutory rate of 35% for the six months ended June 30, 2017. The effective tax rate for the six months ended June 30, 2018 differs from the federal statutory rate of 21% because of the effect in the mix of U.S. and foreign incomes, state income taxes, tax credits and the impact of a contract settlement. The contract settlement resulted in a tax benefit of $5.7 million, which is treated as a discrete item. The effective tax rate during the six months ended June 30, 2018 also included a tax benefit of $11.2 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. The effective tax rate for the six months ended June 30, 2017 differs from the federal statutory rate of 35% because of the effect the mix of U.S. and foreign incomes, state income taxes, tax credits and impact of the gain on bargain purchase. The tax effect of the gain on bargain purchase is treated as a discrete item part of purchase accounting and is not a component of the income tax provision. The effective tax rate during the six months ended June 30, 2017 also included a material tax benefit of $9.9 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

On December 22, 2017, the Tax Cuts and Jobs Act (the “Tax Act”) was enacted into legislation, which includes a broad range of provisions affecting businesses. The Tax Act significantly revises how companies compute their U.S. corporate tax liability by, among other provisions, reducing the corporate tax rate from 35% to 21% for tax years beginning after December 31, 2017. Our accounting for the Tax Act is incomplete. As noted at year-end, however, we were able to reasonably estimate certain effects and, therefore, recorded provisional adjustments associated with the toll charge on undistributed foreign earnings and profits and revaluation of deferred taxes. We have not made any additional measurement-period adjustments related to these items during the quarter. However, we are continuing to gather additional information to complete our accounting for these items and expect to complete our accounting within the prescribed measurement period.

Income taxes were accrued at an estimated effective tax rate of (8)% and (182)% for the six months ended June 30, 2018 and 2017, respectively. Those rates differ from that computed at the federal statutory rate of 21% for the six months ended June 30, 2018 and the federal statutory rate of 35% for the six months ended June 30, 2017.

The effective tax rate for the six months ended June 30, 2018 differs from the federal statutory rate of 21% because of the effect in the mix of U.S. and foreign incomes, state income taxes, tax credits and the impact of a contract settlement. The contract settlement resulted in a tax benefit of $5.7 million, which is treated as a discrete item. The effective tax rate during the six months ended June 30, 2018 also included a tax benefit of $11.2 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.

The effective tax rate for the six months ended June 30, 2017 differs from the federal statutory rate of 35% because of the effect the mix of U.S. and foreign incomes, state income taxes, tax credits and impact of the gain on bargain purchase. The tax effect of the gain on bargain purchase is treated as a discrete item part of purchase accounting and is not a component of the income tax provision. The effective tax rate during the six months ended June 30, 2017 also included a material tax benefit of $9.9 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.