Summary of Significant Accounting Policies	3 Months Ended
Mar. 31, 2017
Accounting Policies [Abstract]
Accounting Policies and Basis of Presentation	Accounting Policies and Basis of Presentation: The accompanying consolidated financial statements have been prepared in conformity with the Financial Accounting Standards Board's ("FASB") Accounting Standards Codification ("ASC") of accounting principles generally accepted in the United States of America ("GAAP"). These interim financial statements should be read in conjunction with these notes and those included in the Company's 2016 Annual Report on Form 10-K incorporated herein by reference. Pertinent accounting and disclosure pronouncements issued from time to time by the FASB are adopted by the Company as they become effective. In 2016, the Company adopted FASB guidance requiring additional disclosures about short-duration insurance contracts which provide additional information about insurance liabilities including the nature, amount, timing, and uncertainty of future cash flows related to those liabilities. The related interim disclosure requirements outlined in the guidance have been included in the pertinent note herein. Effective January 1, 2017, the company adopted new FASB guidance on accounting for share-based payment award transactions. The Company's adoption of this guidance did not have a material impact on the consolidated financial statements. In May 2014, the FASB issued a comprehensive revenue recognition standard which will be effective in 2018 and applies to all entities that have contracts with customers, except for those that fall within the scope of other standards, such as insurance contracts. In January 2016, the FASB issued guidance on the recognition and measurement of financial instruments which will be effective in 2018. Among other changes, the standard will require equity investments to be measured at fair value with changes in fair value recognized in the consolidated statement of income. In February 2016, the FASB issued guidance on lease accounting which will be effective in 2019 and requires balance sheet recognition of all leases with a term of greater than 12 months. Most recently, in June 2016, the FASB issued guidance on accounting for credit losses on financial instruments which will be effective in 2020. The guidance will require immediate recognition of expected credit losses for certain financial instruments and also modifies the impairment model for available for sale debt securities. The Company is currently evaluating the foregoing guidance to determine the potential impact of its adoption on its consolidated financial statements. The financial accounting and reporting process relies on estimates and on the exercise of judgment. In the opinion of management all adjustments consisting only of normal recurring accruals necessary for a fair presentation of the results have been recorded for the interim periods. Amounts shown in the consolidated financial statements and applicable notes are stated (except as otherwise indicated and as to share data) in millions, which amounts may not add to totals shown due to truncation. Necessary reclassifications are made in prior periods' financial statements whenever appropriate to conform to the most current presentation.

Accounting Policies and Basis of Presentation:

The accompanying consolidated financial statements have been prepared in conformity with the Financial Accounting Standards Board's ("FASB") Accounting Standards Codification ("ASC") of accounting principles generally accepted in the United States of America ("GAAP"). These interim financial statements should be read in conjunction with these notes and those included in the Company's 2016 Annual Report on Form 10-K incorporated herein by reference.

Pertinent accounting and disclosure pronouncements issued from time to time by the FASB are adopted by the Company as they become effective. In 2016, the Company adopted FASB guidance requiring additional disclosures about short-duration insurance contracts which provide additional information about insurance liabilities including the nature, amount, timing, and uncertainty of future cash flows related to those liabilities. The related interim disclosure requirements outlined in the guidance have been included in the pertinent note herein. Effective January 1, 2017, the company adopted new FASB guidance on accounting for share-based payment award transactions. The Company's adoption of this guidance did not have a material impact on the consolidated financial statements. In May 2014, the FASB issued a comprehensive revenue recognition standard which will be effective in 2018 and applies to all entities that have contracts with customers, except for those that fall within the scope of other standards, such as insurance contracts. In January 2016, the FASB issued guidance on the recognition and measurement of financial instruments which will be effective in 2018. Among other changes, the standard will require equity investments to be measured at fair value with changes in fair value recognized in the consolidated statement of income. In February 2016, the FASB issued guidance on lease accounting which will be effective in 2019 and requires balance sheet recognition of all leases with a term of greater than 12 months. Most recently, in June 2016, the FASB issued guidance on accounting for credit losses on financial instruments which will be effective in 2020. The guidance will require immediate recognition of expected credit losses for certain financial instruments and also modifies the impairment model for available for sale debt securities. The Company is currently evaluating the foregoing guidance to determine the potential impact of its adoption on its consolidated financial statements.

The financial accounting and reporting process relies on estimates and on the exercise of judgment. In the opinion of management all adjustments consisting only of normal recurring accruals necessary for a fair presentation of the results have been recorded for the interim periods. Amounts shown in the consolidated financial statements and applicable notes are stated (except as otherwise indicated and as to share data) in millions, which amounts may not add to totals shown due to truncation. Necessary reclassifications are made in prior periods' financial statements whenever appropriate to conform to the most current presentation.