Income Taxes	3 Months Ended
Mar. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The effective tax rate was 21% and 253% for the three months ended March 31, 2019 and 2018. During the three months ended March 31, 2018, the Company decided to elect to treat its two most significant U.K. subsidiaries as domestic corporations for U.S. tax purposes. As a result, the earnings and profits of those subsidiaries are no longer considered to be indefinitely reinvested, and during the three months ended March 31, 2018, the Company recorded a one-time deferred tax charge of $99.5 million related to the book and tax basis differences attributable to those subsidiaries. This tax charge represented 232% of the 2018 effective tax rate. The Company uses the estimated annual effective tax rate method for calculating its tax provision in interim periods. This method applies the Company's best estimate of the effective tax rate expected for the full year to year-to-date earnings before income taxes. Certain items, including those deemed to be unusual, infrequent or that cannot be reliably estimated (discrete items), are excluded from the estimated annual effective tax rate and the related tax expense or benefit is reported in the same period as the related item. The Company's estimated annual effective tax rate, which excludes the tax attributable to the change in tax status of the two U.K. subsidiaries recorded in the first quarter of 2018, was 19% for both the three months ended March 31, 2019 and 2018. For both periods, the estimated annual effective tax rate differs from the U.S. statutory tax rate of 21% primarily as a result of tax-exempt investment income.

Income Taxes

The effective tax rate was 21% and 253% for the three months ended March 31, 2019 and 2018. During the three months ended March 31, 2018, the Company decided to elect to treat its two most significant U.K. subsidiaries as domestic corporations for U.S. tax purposes. As a result, the earnings and profits of those subsidiaries are no longer considered to be indefinitely reinvested, and during the three months ended March 31, 2018, the Company recorded a one-time deferred tax charge of $99.5 million related to the book and tax basis differences attributable to those subsidiaries. This tax charge represented 232% of the 2018 effective tax rate.

The Company uses the estimated annual effective tax rate method for calculating its tax provision in interim periods. This method applies the Company's best estimate of the effective tax rate expected for the full year to year-to-date earnings before income taxes. Certain items, including those deemed to be unusual, infrequent or that cannot be reliably estimated (discrete items), are excluded from the estimated annual effective tax rate and the related tax expense or benefit is reported in the same period as the related item. The Company's estimated annual effective tax rate, which excludes the tax attributable to the change in tax status of the two U.K. subsidiaries recorded in the first quarter of 2018, was 19% for both the three months ended March 31, 2019 and 2018. For both periods, the estimated annual effective tax rate differs from the U.S. statutory tax rate of 21% primarily as a result of tax-exempt investment income.