Income Taxes	9 Months Ended
Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The effective income tax rates were 21.9% and 31.7% for the three months ended September 30, 2018 and 2017, respectively. The effective income tax rates were 20.6% and 32.0% for the nine months ended September 30, 2018 and 2017, respectively. The Tax Cuts and Jobs Act (the "Act") was enacted on December 22, 2017. The Act reduces the U.S. federal corporate income tax rate from 35.0% to 21.0%, requires companies to pay a one-time transition tax on earnings of foreign subsidiaries that were previously tax deferred, and creates new taxes on certain foreign-sourced earnings. The Company applied the guidance in Staff Accounting Bulletin 118 ("SAB 118") when accounting for the enactment-date effects of the Act. As of September 30, 2018, the Company finalized its calculations related to the tax effects of the Act and there were no significant changes to the impacts estimated as part of the year ended 2017 provision for income taxes. The effective income tax rate for the three months ended September 30, 2018 was slightly higher than the U.S. federal income tax rate of 21.0% primarily due to an unfavorable $1.0 million adjustment to the SAB 118 deferred tax asset impairment estimate and the impact of state income taxes, partially offset by excess tax benefits from share-based compensation of $0.5 million, a favorable $0.2 million adjustment to the SAB 118 transition tax estimate, and the impact of foreign operations. The effective income tax rate for the nine months ended September 30, 2018 was lower than the U.S. federal income tax rate of 21.0% due to excess tax benefits from share-based compensation of $4.0 million, a favorable $0.2 million adjustment to the SAB 118 transition tax estimate, and the impact of foreign operations, partially offset by an unfavorable $1.0 million adjustment to the SAB 118 deferred tax asset impairment estimate and the impact of state income taxes. The effective income tax rate for the three and nine months ended September 30, 2017 was lower than the U.S. federal income tax rate of 35.0% due to excess tax benefits from share-based compensation of $0.9 million and $2.7 million, respectively, and the impact of foreign operations, partially offset by state income taxes. The Act subjects a U.S. shareholder to a minimum tax on “global intangible low-taxed income” ("GILTI") earned by certain foreign subsidiaries. The FASB Staff Q&A, Topic 740 No. 5, Accounting for Global Intangible Low-Taxed Income, states that an entity can make an accounting policy election to either recognize deferred taxes for temporary differences expected to reverse as GILTI in future years or provide for the tax expense related to GILTI resulting from those items in the year the tax is incurred. The Company has elected to recognize the resulting tax on GILTI as a period expense in the period the tax is incurred and expects to incur tax for the year ended December 31, 2018. Due to the recent changes resulting from the Act, the Company has implemented a new foreign dividend policy effective during the quarter ended September 30, 2018. As a result of the new policy, the Company intends to limit any future foreign distributions to income which has been previously subject to US taxation, for which relevant taxes have been recorded. Nonetheless, the Company will continue to assert that any other outside basis difference of the foreign subsidiaries will be permanently (or indefinitely) reinvested outside of the U.S. Consequently, the Company will not record any additional deferred taxes for this item in 2018.

Income Taxes

The effective income tax rates were 21.9% and 31.7% for the three months ended September 30, 2018 and 2017, respectively. The effective income tax rates were 20.6% and 32.0% for the nine months ended September 30, 2018 and 2017, respectively.

The Tax Cuts and Jobs Act (the "Act") was enacted on December 22, 2017. The Act reduces the U.S. federal corporate income tax rate from 35.0% to 21.0%, requires companies to pay a one-time transition tax on earnings of foreign subsidiaries that were previously tax deferred, and creates new taxes on certain foreign-sourced earnings. The Company applied the guidance in Staff Accounting Bulletin 118 ("SAB 118") when accounting for the enactment-date effects of the Act. As of September 30, 2018, the Company finalized its calculations related to the tax effects of the Act and there were no significant changes to the impacts estimated as part of the year ended 2017 provision for income taxes.

The effective income tax rate for the three months ended September 30, 2018 was slightly higher than the U.S. federal income tax rate of 21.0% primarily due to an unfavorable $1.0 million adjustment to the SAB 118 deferred tax asset impairment estimate and the impact of state income taxes, partially offset by excess tax benefits from share-based compensation of $0.5 million, a favorable $0.2 million adjustment to the SAB 118 transition tax estimate, and the impact of foreign operations.

The effective income tax rate for the nine months ended September 30, 2018 was lower than the U.S. federal income tax rate of 21.0% due to excess tax benefits from share-based compensation of $4.0 million, a favorable $0.2 million adjustment to the SAB 118 transition tax estimate, and the impact of foreign operations, partially offset by an unfavorable $1.0 million adjustment to the SAB 118 deferred tax asset impairment estimate and the impact of state income taxes.

The effective income tax rate for the three and nine months ended September 30, 2017 was lower than the U.S. federal income tax rate of 35.0% due to excess tax benefits from share-based compensation of $0.9 million and $2.7 million, respectively, and the impact of foreign operations, partially offset by state income taxes.

The Act subjects a U.S. shareholder to a minimum tax on “global intangible low-taxed income” ("GILTI") earned by certain foreign subsidiaries. The FASB Staff Q&A, Topic 740 No. 5, Accounting for Global Intangible Low-Taxed Income, states that an entity can make an accounting policy election to either recognize deferred taxes for temporary differences expected to reverse as GILTI in future years or provide for the tax expense related to GILTI resulting from those items in the year the tax is incurred. The Company has elected to recognize the resulting tax on GILTI as a period expense in the period the tax is incurred and expects to incur tax for the year ended December 31, 2018.

Due to the recent changes resulting from the Act, the Company has implemented a new foreign dividend policy effective during the quarter ended September 30, 2018. As a result of the new policy, the Company intends to limit any future foreign distributions to income which has been previously subject to US taxation, for which relevant taxes have been recorded. Nonetheless, the Company will continue to assert that any other outside basis difference of the foreign subsidiaries will be permanently (or indefinitely) reinvested outside of the U.S. Consequently, the Company will not record any additional deferred taxes for this item in 2018.