General (Policies)	12 Months Ended
General (Policies)	Dec. 31, 2017
Accounting Policies [Abstract]
Management's responsibility	Management’s responsibility. The accompanying consolidated financial statements were prepared by management, who is responsible for their integrity and objectivity. The financial statements have been prepared in conformity with U.S. generally accepted accounting principles (GAAP), including management’s best judgments and estimates. Actual results could differ from those estimates.
Reclassifications	Reclassifications. Certain prior year amounts in these consolidated financial statements have been reclassified for comparative purposes. Net income (loss) attributable to Stewart and stockholders’ equity, as previously reported, were not affected.
Consolidation	Consolidation. The consolidated financial statements include all subsidiaries in which the Company owns more than 50% voting rights in electing directors. All significant intercompany amounts and transactions have been eliminated and provisions have been made for noncontrolling interests. Unconsolidated investees, in which the Company typically owns 20% through 50% of the entity, are accounted for by the equity method.
Statutory accounting	Statutory accounting. Stewart Title Guaranty Company (Guaranty) and other title insurance underwriters owned by the Company prepare financial statements in accordance with statutory accounting practices prescribed or permitted by regulatory authorities. In conforming the statutory financial statements to GAAP, statutory premium reserves and reserves for known title losses are eliminated and, in substitution, amounts are established for estimated title losses (Note 1F), for which the net effect, after providing for income taxes, is included in the consolidated statements of operations and comprehensive income (loss). Additionally, the investments in debt securities available-for-sale, which are carried at amortized cost for statutory accounting, are reported at fair value and the net unrealized gains and losses, net of applicable deferred taxes, on the investments are included as a component of accumulated other comprehensive income (loss) within stockholders’ equity.
Revenue recognition	Revenue recognition. Operating revenues from direct title operations are considered earned at the time of the closing of the related real estate transaction. The Company recognizes premium revenues on title insurance policies written by independent agencies (agencies) when the policies are reported to the Company. In addition, where reasonable estimates can be made, the Company accrues for policies issued but not reported until after period end. The Company believes that reasonable estimates can be made when recent and consistent policy issuance information is available. Estimates are based on historical reporting patterns and other information obtained about agencies, as well as current trends in direct operations and in the title industry. In this accrual, future transactions are not being estimated. The Company is estimating revenues on policies that have already been issued by agencies but not yet reported to or received by the Company. The Company has consistently followed the same basic method of estimating unreported policy revenues for more than 10 years. Revenues generated by the Company's ancillary services operations are generally considered earned at the time the related service is performed or the product is delivered to the customer.
Title losses and related claims	Title losses and related claims. The Company’s method for recording reserves for title losses on both an interim and annual basis begins with the calculation of its current loss provision rate, which is applied to the Company’s current premiums resulting in a title loss expense for the period. This loss provision rate is set to provide for estimated losses on current year policies and is determined using moving average ratios of recent actual policy loss payment experience (net of recoveries) to premium revenues. At each quarter end, the Company’s recorded reserve for title losses begins with the prior period’s reserve balance for claim losses, adds the current period provision to that balance and subtracts actual paid claims, resulting in an amount that management compares to its actuarially-based calculation of the ending reserve balance necessary to provide for future reported title losses. The actuarially-based calculation is a paid loss development calculation where loss development factors are selected based on company data and input from the Company’s third-party actuaries. The Company also obtains input from third-party actuaries in the form of a reserve analysis utilizing generally accepted actuarial methods. While the Company is responsible for determining its loss reserves, it utilizes this actuarial input to assess the overall reasonableness of its reserve estimation. If the Company’s recorded reserve amount is not at the third-party actuarial point estimate, but is within a reasonable range (+5.0%/-4.0%) of its actuarially-based reserve calculation and the actuary’s point estimate, the Company’s management assesses the major factors contributing to the different reserve estimates in order to determine the overall reasonableness of its recorded reserve, as well as the position of the recorded reserves relative to the point estimate and the estimated range of reserves. The major factors considered can change from period to period and include items such as current trends in the real estate industry (which management can assess although there is a time lag in the development of this data for use by the actuary), the size and types of claims reported and changes in the Company’s claims management process. If the recorded amount is not within a reasonable range of the Company’s third-party actuary’s point estimate, the Company will adjust the recorded reserves in the current period and reassess the provision rate on a prospective basis. Once the Company’s reserve for title losses is recorded, it is reduced in future periods as a result of claims payments and may be increased or reduced by revisions to the Company’s estimate of the overall level of required reserves. Large claims (those exceeding $1.0 million on a single claim), including large title losses due to independent agency defalcations, are analyzed and reserved for separately due to the higher dollar amount of loss, lower volume of claims reported and sporadic reporting of such claims. Due to the inherent uncertainty in predicting future title policy losses, significant judgment is required by both the Company’s management and its third party actuaries in estimating reserves. As a consequence, the Company’s ultimate liability may be materially greater or less than its current reserves and/or its third party actuary’s calculated estimate.
Cash equivalents	Cash equivalents. Cash equivalents are highly liquid investments with insignificant interest rate risks and maturities of three months or less at the time of acquisition.
Short-term investments	Short-term investments. Short-term investments comprise time deposits with banks, federal government obligations and other investments maturing in less than one year.
Investments in debt and equity securities	Investments in debt and equity securities. The investment portfolio is classified as available-for-sale. Realized gains and losses on sales of investments are determined using the specific identification method. Net unrealized gains and losses on investments available-for-sale, net of applicable deferred taxes, are included as a component of accumulated other comprehensive income (loss) within stockholders’ equity. At the time unrealized gains and losses become realized, they are reclassified from accumulated other comprehensive income (loss) using the specific identification method. Other-than-temporary declines in fair values of investments available-for-sale are charged to income.
Property and equipment	Property and equipment. Depreciation is principally computed using the straight-line method using the following estimated useful lives: buildings – 30 to 40 years and furniture and equipment – 3 to 10 years. Maintenance and repairs are expensed as incurred while improvements are capitalized. Gains and losses are recognized at disposal.
Title plants	Title plants. Title plants include compilations of a county’s official land records, prior title examination files, copies of prior title policies, maps and related materials that are geographically indexed to a specific property. The costs of acquiring existing title plants and creating new ones, prior to the time such plants are placed in operation, are capitalized. Title plants are not amortized since there is no indication of any loss of value over time but are subject to review for impairment. The costs of maintaining and operating title plants are expensed as incurred. Gains and losses on sales of copies of title plants or interests in title plants are recognized at the time of sale.
Goodwill	Goodwill. Goodwill is not amortized, but is reviewed annually during the third quarter using June 30 balances, or whenever occurrences of events indicate a potential impairment at the reporting unit level. The Company evaluates goodwill based on four reporting units with goodwill balances - direct operations, agency operations, international operations and ancillary services. Under GAAP, the Company has an option to assess qualitative factors to determine whether it is more-likely-than-not that the fair value of a reporting unit is less than its carrying amount. In performing the qualitative assessment, the Company considers factors that include macroeconomic conditions, industry and market considerations, overall actual and expected financial performance, market perspective on the Company, as well as other relevant events and circumstances determined by management. The Company evaluates the weight of each factor to determine whether an impairment more-likely-than-not exists. If the Company decides not to use a qualitative assessment or if the reporting unit fails the qualitative assessment, the quantitative impairment analysis is performed. The quantitative analysis involves the comparison of the fair value of each reporting unit to its carrying amount. The goodwill impairment is calculated as the excess of the reporting unit's carrying amount over the estimated fair value and is charged to current operations. While the Company is responsible for assessing whether an impairment of goodwill exists, inputs from third-party appraisers are utilized in performing the quantitative analysis. The Company estimates the fair value using a combination of the income approach (discounted cash flow (DCF) technique) and the market approach (guideline company and precedent transaction analyses). The DCF model utilizes historical and projected operating results and cash flows, initially driven by estimates of changes in future revenue levels, and risk-adjusted discount rates. Projected operating results are primarily driven by anticipated mortgage originations, which are obtained from projections by industry experts, for the title reporting units and expected contractual revenues for the ancillary services reporting unit. Fluctuations in revenues, followed by the ability to appropriately adjust employee count and other operating expenses, or large and unanticipated adjustments to title loss reserves, are the primary reasons for increases or decreases in the projected operating results. Market-based valuation methodologies utilize (i) market multiples of earnings and/or other operating metrics of comparable companies and (ii) the Company's market capitalization and a control premium based on market data and factors specific to ownership and corporate governance structure. Goodwill is assigned to the reporting units at the time the goodwill is initially recorded. Once assigned to a reporting unit, the goodwill is pooled and no longer attributable to a specific acquisition. All activities within a reporting unit are available to support the carrying value of the goodwill. When a business component within a reporting unit is disposed, goodwill is allocated to the component based on the ratio of the component's fair value over the total fair value of the reporting unit.
Other intangibles	Other intangibles. Other intangible assets are comprised principally of non-compete, underwriting and customer relationship agreements and acquired software. Intangible assets are amortized over their estimated lives, which are primarily 3 to 10 years. These intangible assets are reviewed for impairment when certain events or changes in circumstances occur that indicate that the carrying amount of an asset may not be recoverable. The Company performs an analysis to determine whether the carrying amount of each intangible asset is recoverable. The carrying amount is not recoverable when it exceeds the sum of the undiscounted cash flows expected to result from the use and eventual disposition of the asset. For any intangible asset that is not recoverable, the Company calculates the excess of the carrying amount of the intangible asset over its fair value, estimated using the income approach (DCF technique). The resulting difference of the carrying amount over the fair value is treated as the impairment of the asset and is charged to current operations.
Other long-lived assets	Other long-lived assets. The Company reviews the carrying values of title plants and other long-lived assets if certain events occur that may indicate impairment. An impairment of these long-lived assets is indicated when projected undiscounted cash flows over the estimated lives of the assets are less than carrying values. If impairment is indicated, the recorded amounts are written down to fair values.
Fair values	Fair values. The fair values of financial instruments, including cash and cash equivalents, short-term investments, notes receivable, notes payable and accounts payable, are determined by the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal, or most advantageous, market for the asset or liability in an orderly transaction between market participants at the measurement date. The net fair values of these financial instruments approximate their carrying values. Investments in debt and equity securities and certain financial instruments are carried at their fair values.
Leases	Leases. The Company recognizes rent expense under noncancelable operating leases, which generally expire over the next 10 years, on the straight-line basis over the terms of the leases, including provisions for any free rent periods or escalating lease payments.
Income taxes	Income taxes. Deferred tax assets and liabilities are recognized for future tax consequences attributable to differences between the tax basis and the book carrying values of certain assets and liabilities. To the extent that the Company does not believe its deferred tax assets meet the more-likely-than-not realization criteria, it establishes a valuation allowance. When it establishes a valuation allowance, or increases (decreases) the allowance during the year, it records a tax expense (benefit) in its consolidated statements of operations and comprehensive income (loss). Enacted tax rates are used in calculating amounts. The Company provides for uncertainties in income taxes by prescribing a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return.
Recently adopted accounting pronouncements and Recent significant accounting pronouncements not yet adopted	Recently adopted accounting pronouncements. In January 2017, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2017-01, Business Combination: Clarifying the Definition of a Business. The amendments in this ASU change the definition of a business to assist with evaluating when a set of transferred assets and activities is a business. This ASU is effective for annual and interim periods beginning after December 15, 2017 and early adoption is allowed. The Company early adopted ASU 2017-01 effective January 1, 2017. Also in January 2017, the FASB issued ASU 2017-04, Intangibles - Goodwill and Other: Simplifying the Test for Goodwill Impairment. To simplify the subsequent measurement of goodwill, the amendments in this ASU eliminate Step 2 from the two-step quantitative goodwill impairment test. Under this new guidance, the annual, or interim, goodwill impairment test is performed by comparing the fair value of a reporting unit with its carrying amount. An impairment charge, if determined applicable, should be recognized for the amount by which the carrying amount exceeds the reporting unit’s fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. In addition, income tax effects from any tax deductible goodwill on the carrying amount of the reporting unit should be considered when measuring the goodwill impairment loss. This ASU does not amend the optional qualitative assessment of goodwill impairment. This ASU is effective for annual and interim periods beginning after December 15, 2019 and early adoption is allowed. The Company early adopted ASU 2017-04 effective January 1, 2017. The adoption did not result in any impact in 2017. In May 2017, the FASB issued ASU 2017-09, Compensation - Stock Compensation: Scope of Modification Accounting, to clarify when to account for a change to the terms or conditions of a share-based payment award as a modification. Under the new standard, modification is required only if the fair value, the vesting conditions, or the classification of an award as equity or liability changes as a result of the change in terms or conditions. This ASU is effective for annual and interim periods beginning after December 15, 2017, with prospective application, and early adoption is allowed. The Company early adopted ASU 2017-09 effective June 1, 2017. The adoption did not result in any impact in 2017. S. Recent significant accounting pronouncements not yet adopted. In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers, which eliminated the transaction-specific and industry-specific revenue recognition guidance under current GAAP and replaced it with a principles-based approach for determining revenue recognition. The new guidance sets forth the steps to be followed to recognize revenue: (i) identify the contract(s) with a customer, (ii) identify the performance obligations in the contract, (iii) determine the transaction price, (iv) allocate the transaction price to the performance obligations in the contract, and (v) recognize revenue when (or as) the entity satisfies a performance obligation. ASU 2014-09 is effective on annual and interim periods beginning after December 15, 2017. The Company adopted ASU 2014-09 on January 1, 2018 and will utilize the cumulative effect method of adoption for its disclosures beginning the first quarter 2018. Based on management's assessment, the Company determined that ASU 2014-09, other than certain additional footnote disclosures, does not materially impact the accounting or reporting of the Company's revenue streams. In February 2016, the FASB issued ASU 2016-02, Leases, which updated the current guidance related to leases. The new guidance includes the requirement for the lessee to recognize in the balance sheet a liability equal to the present value of contractual lease payments with terms of more than twelve months and a right-of-use asset representing the right to use the underlying asset for the lease term. Disclosures will be required by lessees to meet the objective of enabling users of financial statements to assess the amount, timing, and uncertainty of cash flows arising from leases. This ASU is effective for annual and interim periods beginning after December 15, 2018 and early adoption is allowed. The Company expects to adopt ASU 2016-02 on January 1, 2019 using the modified retrospective approach. The Company expects the adoption of ASU 2016-02 will result in material increases in the assets and liabilities reported on its consolidated balance sheets. As disclosed in Note 16, the undiscounted future contractual lease payments with terms of more than twelve months were approximately $167.1 million as of December 31, 2017. The Company expects the new ASU will likely have an insignificant impact on its consolidated statements of operations and cash flows. The Company is currently evaluating certain lease management and accounting systems and plans to begin system customization and implementation by mid 2018.