Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2017

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of New Accounting Pronouncements

Accounting Updates Adopted in 2017:

Accounting Standards Codification (ASC)	Description	Date of Adoption	Effect on Financial Statements
ASC 944 "Financial Services - Insurance"	This update changed the disclosure requirements for certain insurance contracts. These changes included a requirement to disclose the rollforward of the liability for unpaid claims and claim adjustment expenses in both interim and annual reporting periods for long-duration and short-duration insurance contracts. Additional claims disclosures were also required for short-duration contracts. The guidance is to be applied retrospectively.	January 1, 2016 for annual reporting period disclosures and January 1, 2017 for interim reporting period disclosures.	The adoption of this update expanded our interim reporting period disclosures but had no effect on our financial position or results of operations. The annual reporting period disclosure requirements were only applicable to our individual dental products, which we deem immaterial, and therefore did not alter our annual disclosures.
ASC 718 "Compensation - Stock Compensation"	This update changed the accounting and disclosure requirements for certain aspects of share-based payments to employees. The update required all income tax effects of stock-based compensation awards to be recognized in the income statement when the awards vest or are settled. The update also allows an employer to repurchase more of an employee's shares than it can today for tax withholding purposes without triggering liability accounting and to make a policy election to account for forfeitures as they occur. Additionally, the update required reclassification of tax-related cash flows resulting from share-based payments to be classified as operating activities instead of financing activities on the statement of cash flows. Transition guidance for the amendments varies between the retrospective, modified retrospective, and prospective methods depending on the specific requirement of the update.	January 1, 2017	The adoption of this update did not have a material effect on our financial position or results of operations. The impact of the update reduced our effective income tax rate by a de minimis amount for the year ended December 31, 2017. During periods in which the vesting date fair value differs from the grant date fair value of certain stock-based compensation awards, we may experience volatility in the income tax recognized in our results of operations. The amendment related to the reclassification of tax-related cash flows in our consolidated statements of cash flows has been applied prospectively.

Accounting Updates Adopted in 2016:

ASC	Description	Date of Adoption	Effect on Financial Statements
ASC 820 "Fair Value Measurement"	This update eliminated the requirement to categorize within the fair value hierarchy table investments whose fair value is measured at net asset value using the practical expedient. Instead, entities are required to disclose the fair value of these investments so that financial statement users can reconcile amounts reported in the fair value hierarchy table to the amounts reported on the consolidated balance sheets. The guidance is to be applied retrospectively.	January 1, 2016	The adoption of this update modified certain of our annual reporting period disclosures for invested assets held in our employee benefit plans but had no effect on our financial position or results of operations.
ASC 835 "Interest - Imputation of Interest"	This update simplified the presentation of deferred debt issuance costs by requiring these costs to be presented in the balance sheet as a reduction of the carrying amount of the debt liability to which the deferred costs relate, rather than classifying the deferred costs as an asset. This classification is consistent with the treatment of debt discounts. We applied the amendments in the update retrospectively, adjusting all prior periods in our consolidated financial statements and accompanying notes.	January 1, 2016	The adoption of this update resulted in reclassification adjustments to our consolidated balance sheets but had no effect on our financial position or results of operations.

Accounting Updates Adopted in 2015:

ASC	Description	Date of Adoption	Effect on Financial Statements
ASC 860 "Transfers and Servicing"	This update changed the accounting for repurchase-to-maturity transactions and linked repurchase financings to secured borrowing accounting, which is consistent with the accounting for other repurchase agreements. The update also required disclosures for repurchase agreements, securities lending transactions, and repurchase-to-maturity transactions.	January 1, 2015, except for certain disclosures, which were effective April 1, 2015.	The adoption of this update expanded our disclosures, but had no effect on our financial position or results of operations.
ASC 323 "Investments - Equity Method and Joint Ventures"	This update permitted entities to make an accounting policy election to account for investments in qualified affordable housing projects using the proportional amortization method if certain conditions are met. Under the proportional amortization method, an entity amortizes the initial cost of the investment in proportion to the tax credits and other tax benefits received and recognizes the net investment performance in the income statement as a component of income tax expense (benefit). Additional disclosures concerning investments in qualified affordable housing projects were also required.	January 1, 2015	The adoption of this update resulted in the retrospective adjustment of all prior periods in our consolidated financial statements and accompanying notes.