| **Accounting Policies Pending Accounting Updates (Policies)** | 6 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         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| **Accounting Policies [Abstract]**                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                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| Adopted Accounting Updates and Pending Accounting Updates     | Adopted Accounting UpdatesASU 2016-07, Investments - Equity Method and Joint Ventures (Topic 323): Simplifying the Transition to the Equity Method of AccountingIn March 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2016-07, Equity Method and Joint Ventures (Topic 323): Simplifying the Transition to the Equity Method of Accounting. ASU 2016-07 eliminates the requirement to retroactively adjust an investment, results of operations, and retained earnings once an investment qualifies for use of the equity method. It requires the equity method investor to add the cost of acquiring the additional interest in the investee to the current basis of the investor's previously held interest and adopt the equity method of accounting as of the date the investment becomes qualified for equity method accounting without retroactive adjustment. The effective date of ASU 2016-07 was for interim and annual reporting periods beginning after December 15, 2016, and was applied prospectively. The company adopted this ASU effective January 1, 2017, and it did not have a material impact on our company's consolidated financial position, cash flows or results of operations.ASU 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment AccountingIn March 2016, the FASB issued ASU 2016-09, Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting. ASU 2016-09 simplifies several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. The effective date of ASU 2016-09 was for interim and annual reporting periods beginning after December 15, 2016. The recognition and classification of the excess tax benefit provisions were applied prospectively in the results of operations and statement of cash flows. This adoption resulted in excess tax benefits of $6 million, which reduced our current provision for income taxes in our results of operations for both the three and six months ended June 30, 2017, respectively. The statutory tax withholding classification, which are cash payments made to taxing authorities for shares withheld, were applied retrospectively and reclassified the statutory tax withholding requirements in the statement of cash flows from Other liabilities in operating activities to Other in financing activities. This statutory tax withholding reclassification resulted in $12 million and $9 million being included in financing activities for the six months ended June 30, 2017 and 2016, respectively. There were no cumulative effect adjustments upon adoption of this ASU. Pending Accounting UpdatesASU 2014-09 Revenue from Contracts with Customers In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers. ASU 2014-09 requires an entity to recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods and services. Insurance contracts do not fall within the scope of this ASU. The effective date of ASU 2014-09 is for interim and annual reporting periods beginning after December 15, 2017. The ASU has not yet been adopted and will not have a material impact on our company’s financial position, cash flows or results of operations.ASU 2016-01, Financial Instruments - Overall (Subtopic 825-10) - Recognition and Measurement of Financial Assets and Financial LiabilitiesIn January 2016, the FASB issued ASU 2016-01, Financial Instruments - Overall (Subtopic 825-10) - Recognition and Measurement of Financial Assets and Financial Liabilities. ASU 2016-01 revises the accounting related to the classification and measurement of investments in equity securities and the presentation of certain fair value changes for financial liabilities measured at fair value. Our results of operations will be impacted as changes in fair value of equity securities will be reported in net income instead of reported in other comprehensive income. The effective date of ASU 2016-01 is for interim and annual reporting periods beginning after December 15, 2017 and will be applied prospectively. The ASU has not yet been adopted. Had we adopted this ASU on June 30, 2017, $1.677 billion of after-tax unrealized gains on equity securities would have been reclassified from accumulated other comprehensive income to retained earnings. The actual amount reclassified upon adoption will vary depending on the future changes in fair value of our equity portfolio. ASU 2016-02, Leases (Topic 842)In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). The main provision of ASU 2016-02 requires the recognition of lease assets and lease liabilities by lessees for those leases classified as operating leases under previous GAAP. The effective date of ASU 2016-02 is for interim and annual reporting periods beginning after December 15, 2018. The ASU has not yet been adopted. Management is currently evaluating the impact on our company’s consolidated financial position, cash flows and results of operations.ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial InstrumentsIn June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. ASU 2016-13 amends previous guidance on the impairment of financial instruments by adding an impairment model that allows an entity to recognize expected credit losses as an allowance rather than impairing as they are incurred. The new guidance is intended to reduce complexity of credit impairment models and result in a more timely recognition of expected credit losses. The effective date of ASU 2016-13 is for interim and annual reporting periods beginning after December 15, 2019. The ASU has not yet been adopted. Management is currently evaluating the impact on our company's consolidated financial position, cash flows or results of operations.ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash PaymentsIn August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments. ASU 2016-15 addresses eight specific cash flow issues with the objective of reducing the existing diversity in practice. The effective date of ASU 2016-15 is for interim and annual reporting periods beginning after December 15, 2017. The ASU has not yet been adopted; however, it is not expected to have a material impact on our company's consolidated financial position, cash flows or results of operations.ASU 2017-07, Compensation - Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit CostIn March 2017, the FASB issued ASU 2017-07, Compensation - Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Postretirement Benefit Costs. ASU 2017-07 provides guidance on how to present the components of net periodic benefit costs in the income statement for pension plans and other post-retirement benefit plans. The effective date of ASU 2017-07 is for interim and annual reporting periods beginning after December 15, 2017. The ASU has not yet been adopted; however, it is not expected to have a material impact on our company's consolidated financial position, cash flows or results of operations.ASU 2017-08, Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt SecuritiesIn March 2017, the FASB issued ASU 2017-08, Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities. ASU 2017-08 amends guidance on the amortization period of premiums on certain purchased callable debt securities. The amendments shorten the amortization period of premiums on certain purchased callable debt securities to the earliest call date. The amendments should be applied on a modified retrospective basis through a cumulative-effect adjustment to beginning retained earnings. The effective date of ASU 2017-08 is for interim and annual reporting periods beginning after December 15, 2018. The ASU has not yet been adopted. Management is currently evaluating the impact on our company's consolidated financial position, cash flows or results of operations.ASU 2017-09, Compensation - Stock Compensation (Topic 718): Scope of Modification AccountingIn May 2017, the FASB issued ASU 2017-09, Compensation - Stock Compensation (Topic 718): Scope of Modification Accounting. ASU 2017-09 clarifies when to account for a change to the terms or conditions of a share-based payment award as a modification. Under the new guidance, modification accounting is required only if the fair value, the vesting conditions, or the classification of the award (as equity or liability) changes as a result of the change in terms or conditions. The amendment should be applied on a prospective basis. The effective date of ASU 2017-09 is for interim and annual reporting periods, beginning after December 15, 2017. The ASU has not yet been adopted; however, it will not have a material impact on our company's consolidated financial position, cash flows or results of operations upon adoption. |

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| - Definition
Disclosure of accounting policy pertaining to new accounting pronouncements that may impact the entity's financial reporting. Includes, but is not limited to, quantification of the expected or actual impact.
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