Income Taxes	3 Months Ended
Mar. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Our expense or benefit from income taxes for interim periods is determined using an estimate of our annual effective tax rate, adjusted for discrete items. During the three months ended March 31, 2017 and 2016, our effective tax rate was 39% and 30%, respectively. The March 31, 2017 effective tax rate was higher than the U.S. Federal income tax rate of 35%, primarily due to state and local income tax, net of Federal income tax benefits, offset by the Federal research credit. The March 31, 2016 effective tax rate was lower than the 35% Federal income tax rate, primarily due to the effect of market adjustments for stock options exercised under our share-based compensation program, non-deductible transaction-related costs incurred in 2016 associated with the Spin-Off, and the Federal research credit. There were no uncertain tax positions as of March 31, 2017 or December 31, 2016.

Income Taxes

3 Months Ended

Mar. 31, 2017

Our expense or benefit from income taxes for interim periods is determined using an estimate of our annual effective tax rate, adjusted for discrete items.

During the three months ended March 31, 2017 and 2016, our effective tax rate was 39% and 30%, respectively. The March 31, 2017 effective tax rate was higher than the U.S. Federal income tax rate of 35%, primarily due to state and local income tax, net of Federal income tax benefits, offset by the Federal research credit. The March 31, 2016 effective tax rate was lower than the 35% Federal income tax rate, primarily due to the effect of market adjustments for stock options exercised under our share-based compensation program, non-deductible transaction-related costs incurred in 2016 associated with the Spin-Off, and the Federal research credit.

There were no uncertain tax positions as of March 31, 2017 or December 31, 2016.