Income Taxes	6 Months Ended
Jun. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Note 9: Income Taxes Management estimates the annual effective income tax rate quarterly, based on current annual forecasted results. Items unrelated to current year ordinary income are recognized entirely in the period identified as a discrete item of tax. The quarterly income tax provision (benefit) is comprised of tax on ordinary income provided at the most recent estimated annual effective tax rate (“ETR”), increased or decreased for the tax effect of discrete items. For the six months ended June 30, 2018 and 2017, our estimated annual effective tax rates applied to ordinary income (losses) were 19.6% and 22.4%, respectively. The difference between the statutory rate and the projected annual ETR of 19.6% for 2018 is primarily due to the research and development credit. Our estimated ETR incorporated the 21% statutory U.S. corporate income tax rate that was enacted on December 22, 2017 by the Tax Cuts and Jobs Act, for the tax years beginning after December 31, 2017. Including the effect of discrete items, our effective tax rates for the six months ended June 30, 2018 and 2017 were 23.7% and 92.2%, respectively. The difference between the annual ETR of 19.6% and the quarterly rate of 23.7% for the six months ended June 30, 2018 is primarily related to the expiration of fully vested stock options, which impacted income tax expense by $0.3 million.

Note 9: Income Taxes

Management estimates the annual effective income tax rate quarterly, based on current annual forecasted results. Items unrelated to current year ordinary income are recognized entirely in the period identified as a discrete item of tax. The quarterly income tax provision (benefit) is comprised of tax on ordinary income provided at the most recent estimated annual effective tax rate (“ETR”), increased or decreased for the tax effect of discrete items.

For the six months ended June 30, 2018 and 2017, our estimated annual effective tax rates applied to ordinary income (losses) were 19.6% and 22.4%, respectively. The difference between the statutory rate and the projected annual ETR of 19.6% for 2018 is primarily due to the research and development credit. Our estimated ETR incorporated the 21% statutory U.S. corporate income tax rate that was enacted on December 22, 2017 by the Tax Cuts and Jobs Act, for the tax years beginning after December 31, 2017.

Including the effect of discrete items, our effective tax rates for the six months ended June 30, 2018 and 2017 were 23.7% and 92.2%, respectively. The difference between the annual ETR of 19.6% and the quarterly rate of 23.7% for the six months ended June 30, 2018 is primarily related to the expiration of fully vested stock options, which impacted income tax expense by $0.3 million.