Income taxes	6 Months Ended
Jun. 30, 2017
Income Tax Disclosure [Abstract]
Income taxes	Note 10. Income taxes The effective income tax rates were 37.8 percent and 37.3 percent for the three months ended June 30, 2017 and 2016, respectively, and 36.6 percent and 36.9 percent for the six months ended June 30, 2017 and 2016, respectively. Total income tax expense for the three and six months ended June 30, 2017 differed from amounts computed by applying the United States federal statutory tax rates to pre-tax income primarily due to state income taxes and the impact of permanent differences between book and taxable income. The Company recorded discrete income tax expense of approximately $2 million and a discrete income tax benefit of approximately $6 million for the three and six months ended June 30, 2017, respectively, related to excess tax deficiencies (benefits) on stock-based awards, which are recorded in the income tax provision pursuant to ASU No. 2016-09, which was adopted on January 1, 2017. Total income tax benefit for the three and six months ended June 30, 2016 differed from amounts computed by applying the United States federal statutory tax rates to pre-tax loss primarily due to state income taxes, partially offset by the impact of permanent differences between book and taxable loss.

Income taxes

6 Months Ended

Jun. 30, 2017

Note 10. Income taxes

The effective income tax rates were 37.8 percent and 37.3 percent for the three months ended June 30, 2017 and 2016, respectively, and 36.6 percent and 36.9 percent for the six months ended June 30, 2017 and 2016, respectively. Total income tax expense for the three and six months ended June 30, 2017 differed from amounts computed by applying the United States federal statutory tax rates to pre-tax income primarily due to state income taxes and the impact of permanent differences between book and taxable income. The Company recorded discrete income tax expense of approximately $2 million and a discrete income tax benefit of approximately $6 million for the three and six months ended June 30, 2017, respectively, related to excess tax deficiencies (benefits) on stock-based awards, which are recorded in the income tax provision pursuant to ASU No. 2016-09, which was adopted on January 1, 2017. Total income tax benefit for the three and six months ended June 30, 2016 differed from amounts computed by applying the United States federal statutory tax rates to pre-tax loss primarily due to state income taxes, partially offset by the impact of permanent differences between book and taxable loss.