Income Taxes	9 Months Ended
Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	6. Income Taxes On December 22, 2017, the legislation commonly referred to as the Tax Cuts and Jobs Act (the “Tax Act”) was enacted into law, which changed various corporate income tax provisions within the existing Internal Revenue Code. The most significant changes that impacted the Company were the reduction in the corporate federal income tax rate from 35% to 21% and 100% bonus depreciation for qualified property acquired and placed in service after September 27, 2017 and before January 1, 2023. Under the guidance set forth in the SEC's Staff Accounting Bulletin No. 118 (“SAB 118”), the Company may record provisional amounts for the impact of the Tax Act. As of September 30, 2018, the Company has finalized its 2017 federal income tax return and as such completed the accounting for the income tax effects of the 2017 Tax Act. In accordance with SAB 118, any future adjustments required due to changes in interpretation and guidance that may be issued will be recorded as discrete adjustments to income tax expense in the period in which those adjustments become estimable and finalized. The Company’s effective tax rate decreased to 17.3% for the thirteen weeks ended September 30, 2018 from 33.8% for the thirteen weeks ended October 1, 2017 primarily due to the enactment of the Tax Act as disclosed above, as well as the impact of a tax calculation method change. During the quarter ended September 30, 2018 the Company adopted tax calculation method changes that resulted in the accelerated deduction or deferral of certain items. The method changes were included in the Company’s 2017 tax return that was finalized during the fiscal quarter. As a result, the Company recorded a $2.6 million discrete tax benefit in the third quarter of 2018, which decreased the effective tax rate by 5.7%. The Company’s effective tax rate decreased to 16.4% for the thirty-nine weeks ended September 30, 2018 from 31.7% for the thirty-nine weeks ended October 1, 2017 primarily due to the enactment of the Tax Act disclosed above, as well as the recognition of excess tax benefits related to the exercise of stock options recognized in the income tax provision. The tax calculation method change resulted in a discrete rate benefit of 1.5% for the thirty-nine weeks ended September 30, 2018. Excess tax benefits associated with share-based payment awards are recognized as income tax expense or benefit in the statements of income. The tax effects of exercised or vested awards are treated as discrete items in the reporting period in which they occur. The income tax benefits resulting from excess tax benefits of share-based payment awards were $1.0 million and $0.2 million for the thirteen weeks ended September 30, 2018 and October 1, 2017, respectively. The income tax benefits resulting from excess tax benefits of share-based payment awards were $12.4 million and $8.4 million for the thirty-nine weeks ended September 30, 2018 and October 1, 2017, respectively.

6. Income Taxes

On December 22, 2017, the legislation commonly referred to as the Tax Cuts and Jobs Act (the “Tax Act”) was enacted into law, which changed various corporate income tax provisions within the existing Internal Revenue Code. The most significant changes that impacted the Company were the reduction in the corporate federal income tax rate from 35% to 21% and 100% bonus depreciation for qualified property acquired and placed in service after September 27, 2017 and before January 1, 2023.

Under the guidance set forth in the SEC's Staff Accounting Bulletin No. 118 (“SAB 118”), the Company may record provisional amounts for the impact of the Tax Act. As of September 30, 2018, the Company has finalized its 2017 federal income tax return and as such completed the accounting for the income tax effects of the 2017 Tax Act. In accordance with SAB 118, any future adjustments required due to changes in interpretation and guidance that may be issued will be recorded as discrete adjustments to income tax expense in the period in which those adjustments become estimable and finalized.

The Company’s effective tax rate decreased to 17.3% for the thirteen weeks ended September 30, 2018 from 33.8% for the thirteen weeks ended October 1, 2017 primarily due to the enactment of the Tax Act as disclosed above, as well as the impact of a tax calculation method change. During the quarter ended September 30, 2018 the Company adopted tax calculation method changes that resulted in the accelerated deduction or deferral of certain items. The method changes were included in the Company’s 2017 tax return that was finalized during the fiscal quarter. As a result, the Company recorded a $2.6 million discrete tax benefit in the third quarter of 2018, which decreased the effective tax rate by 5.7%.

The Company’s effective tax rate decreased to 16.4% for the thirty-nine weeks ended September 30, 2018 from 31.7% for the thirty-nine weeks ended October 1, 2017 primarily due to the enactment of the Tax Act disclosed above, as well as the recognition of excess tax benefits related to the exercise of stock options recognized in the income tax provision. The tax calculation method change resulted in a discrete rate benefit of 1.5% for the thirty-nine weeks ended September 30, 2018.

Excess tax benefits associated with share-based payment awards are recognized as income tax expense or benefit in the statements of income. The tax effects of exercised or vested awards are treated as discrete items in the reporting period in which they occur. The income tax benefits resulting from excess tax benefits of share-based payment awards were $1.0 million and $0.2 million for the thirteen weeks ended September 30, 2018 and October 1, 2017, respectively. The income tax benefits resulting from excess tax benefits of share-based payment awards were $12.4 million and $8.4 million for the thirty-nine weeks ended September 30, 2018 and October 1, 2017, respectively.