Basis of Presentation (Policies)	9 Months Ended
Basis of Presentation (Policies)	Sep. 30, 2017
Accounting Policies [Abstract]
Basis of Accounting	Loews Corporation is a holding company. Its subsidiaries are engaged in the following lines of business: commercial property and casualty insurance (CNA Financial Corporation (“CNA”), a 89% owned subsidiary); the operation of offshore oil and gas drilling rigs (Diamond Offshore Drilling, Inc. (“Diamond Offshore”), a 53% owned subsidiary); transportation and storage of natural gas and natural gas liquids (Boardwalk Pipeline Partners, LP (“Boardwalk Pipeline”), a 51% owned subsidiary); the operation of a chain of hotels (Loews Hotels Holding Corporation (“Loews Hotels & Co”), a wholly owned subsidiary); and the manufacture of rigid plastic packaging solutions (Consolidated Container Company LLC, a 99% owned subsidiary). Unless the context otherwise requires, the terms “Company,” “Loews” and “Registrant” as used herein mean Loews Corporation excluding its subsidiaries and the term “Net income (loss) attributable to Loews Corporation” as used herein means Net income (loss) attributable to Loews Corporation shareholders. In the opinion of management, the accompanying unaudited Consolidated Condensed Financial Statements reflect all adjustments (consisting of normal recurring accruals) necessary to present fairly the Company’s financial position as of September 30, 2017 and December 31, 2016, results of operations and comprehensive income for the three and nine months ended September 30, 2017 and 2016 and changes in shareholders’ equity and cash flows for the nine months ended September 30, 2017 and 2016. Net income (loss) for the third quarter and first nine months of each of the years is not necessarily indicative of net income (loss) for that entire year. These Consolidated Condensed Financial Statements should be read in conjunction with the Consolidated Financial Statements in the Company’s Annual Report on Form 10-K for the year ended December 31, 2016.
Income Per Share	The Company presents basic and diluted net income (loss) per share on the Consolidated Condensed Statements of Income. Basic net income (loss) per share excludes dilution and is computed by dividing net income (loss) attributable to common stock by the weighted average number of common shares outstanding for the period. Diluted net income per share reflects the potential dilution that could occur if securities or other contracts to issue common stock were exercised or converted into common stock. 0.4 million and 3.3 million shares for the three months ended September 30, 2017 and 2016 and 0.4 million and 4.7 million shares for the nine months ended September 30, 2017 and 2016 attributable to employee stock-based compensation awards were not included in the diluted weighted average shares outstanding amounts because the effect would have been antidilutive.
Accounting changes	Accounting changes – In March of 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standard Update (“ASU”) 2016-09, “Compensation-Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting.” The updated accounting guidance simplifies the accounting for share-based payment award transactions, including income tax consequences and classification on the statement of cash flows. As of January 1, 2017, the Company adopted the updated accounting guidance and began recognizing excess tax benefits or deficiencies on vesting or settlement of awards as an income tax benefit or expense within net income and the related cash flows classified within operating activities. The change impacted the amount and timing of income tax expense recognition as well as the calculation of diluted earnings per share. The accounting change did not have a material effect on the consolidated financial statements.
Recently issued ASUs	Recently issued ASUs – In May of 2014, the FASB issued ASU 2014-09, “Revenue from Contracts with Customers (Topic 606).” The core principle of the new accounting guidance is that a company should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. The new accounting guidance provides a five-step analysis of transactions to determine when and how revenue is recognized and requires enhanced disclosures about revenue. The guidance is effective for interim and annual reporting periods beginning after December 15, 2017, and may be adopted either retrospectively or on a modified basis, with a cumulative effect adjustment to the opening balance sheet at the date of adoption. The Company expects to adopt this updated guidance using the modified retrospective method. The standard excludes from its scope the accounting for insurance contracts, financial instruments and certain other agreements that are subject to other guidance in the FASB Accounting Standards Codification, which limits the impact of this change in accounting for the Company. Upon adoption, the Company expects that revenue on CNA’s warranty products and services will be recognized more slowly than under the current revenue recognition pattern. The Company also expects that Other revenues and operating expenses will increase significantly for CNA’s warranty products to reflect the gross amount paid by consumers to the auto dealers that act as CNA’s agents. While the Company continues to evaluate the effect the guidance will have on its consolidated financial statements, the Company expects the adoption of the updated guidance will not have a material effect on its results of operations or financial position. In January of 2016, the FASB issued ASU 2016-01, “Financial Instruments – Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities.” The updated accounting guidance requires changes to the reporting model for financial instruments. The guidance is effective for interim and annual periods beginning after December 15, 2017. The Company expects the primary change to be the requirement for equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) to be measured at fair value with changes in fair value recognized in net income. Upon adoption, the Company will recognize an adjustment for the cumulative amount of unrealized investment gains and losses related to available-for-sale equity securities within the opening balances of Retained earnings and Accumulated other comprehensive income (loss). The Company expects the adoption of the updated guidance will not have a material effect on its consolidated financial statements. In February of 2016, the FASB issued ASU 2016-02, “Leases (Topic 842).” The updated guidance requires lessees to recognize lease assets and lease liabilities for most operating leases. In addition, the updated guidance requires that lessors separate lease and nonlease components in a contract in accordance with the new revenue guidance in ASU 2014-09. The updated guidance is effective for interim and annual periods beginning after December 15, 2018. The Company is currently evaluating the effect the guidance will have on its consolidated financial statements. In June of 2016, the FASB issued ASU 2016-13, “Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments.” The updated accounting guidance requires changes to the recognition of credit losses on financial instruments not accounted for at fair value through net income. The guidance is effective for interim and annual periods beginning after December 15, 2019. The Company is currently evaluating the effect the guidance will have on its consolidated financial statements, and expects the primary changes to be the use of the expected credit loss model for the mortgage loan portfolio and reinsurance receivables and the presentation of credit losses within the available-for-sale fixed maturities portfolio through an allowance method rather than as a direct write-down. The expected credit loss model will require a financial asset to be presented at the net amount expected to be collected. Under the allowance method for available-for-sale debt securities the Company will record reversals of credit losses if the estimate of credit losses declines. In October of 2016, the FASB issued ASU 2016-16, “Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory.” The updated guidance amends the accounting for the income tax consequences of intra-entity transfers of assets other than inventory. This guidance is effective for interim and annual reporting periods beginning after December 15, 2017. The Company is currently evaluating its historical intra-group transactions for the possible effect of the updated guidance. The Company expects to adopt this updated guidance using the modified retrospective approach with a cumulative effect adjustment to the opening balance of Retained earnings with an offset to a deferred income tax liability.