Income Taxes	6 Months Ended
Jun. 30, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes: The effective income tax rate for the three-month and six-month periods ended June 30, 2019 was 18.2% and 21.2%, respectively, compared to 21.5% and 19.7% for the three-month and six-month periods ended June 30, 2018, respectively. The Company’s effective income tax rate fluctuates based on, among other factors, its level and location of income. The difference between the U.S. federal statutory income tax rate and our effective income tax rate for the three-month and six-month periods ended June 30, 2019 and 2018 was impacted by a variety of factors, primarily stemming from the location in which income was earned. Income tax expense for the three-month and six-month periods ended June 30, 2018 included discrete tax adjustments of $42.0 million for the disposition of the polyolefin catalysts and components portion of our Performance Catalyst Solutions (“PCS”) business (“Polyolefin Catalysts Divestiture”) and $8.5 million for a valuation allowance recorded due to a foreign restructuring plan, partially offset by an $8.0 million benefit for tax accounting method changes. In addition, Income tax expense for the six-month period ended June 30, 2018 included discrete tax benefits related to adjustments recorded for the U.S. Tax Cuts and Jobs Act (“TCJA”) and excess tax benefits realized from stock-based compensation arrangements.

The effective income tax rate for the three-month and six-month periods ended June 30, 2019 was 18.2% and 21.2%, respectively, compared to 21.5% and 19.7% for the three-month and six-month periods ended June 30, 2018, respectively. The Company’s effective income tax rate fluctuates based on, among other factors, its level and location of income. The difference between the U.S. federal statutory income tax rate and our effective income tax rate for the three-month and six-month periods ended June 30, 2019 and 2018 was impacted by a variety of factors, primarily stemming from the location in which income was earned. Income tax expense for the three-month and six-month periods ended June 30, 2018 included discrete tax adjustments of $42.0 million for the disposition of the polyolefin catalysts and components portion of our Performance Catalyst Solutions (“PCS”) business (“Polyolefin Catalysts Divestiture”) and $8.5 million for a valuation allowance recorded due to a foreign restructuring plan, partially offset by an $8.0 million benefit for tax accounting method changes. In addition, Income tax expense for the six-month period ended June 30, 2018 included discrete tax benefits related to adjustments recorded for the U.S. Tax Cuts and Jobs Act (“TCJA”) and excess tax benefits realized from stock-based compensation arrangements.