Accounting Policies (Policies)	9 Months Ended
Dec. 31, 2017
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation: The accompanying unaudited condensed consolidated financial statements (Condensed Consolidated Financial Statements) of CA, Inc. and its subsidiaries (Company) have been prepared in accordance with U.S. generally accepted accounting principles (GAAP), as defined in Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) 270, for interim financial information and in accordance with the instructions to Form 10-Q and Article 10 of Securities and Exchange Commission Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements and therefore should be read in conjunction with the Company’s consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the fiscal year ended March 31, 2017 (2017 Form 10-K). In the opinion of management, all adjustments considered necessary for a fair presentation have been included. All such adjustments are of a normal, recurring nature. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Although these estimates are based on management’s knowledge of current events and actions it may undertake in the future, these estimates may ultimately differ from actual results. Operating results for the three and nine months ended December 31, 2017 are not necessarily indicative of the results that may be expected for the fiscal year ending March 31, 2018.
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted Cash: The Company’s cash and cash equivalents are held in numerous locations throughout the world, with approximately 66% being held by the Company’s foreign subsidiaries outside the United States at December 31, 2017. At December 31, 2017 and March 31, 2017, the total amount of restricted cash included in “Other noncurrent assets, net” in the Company’s Condensed Consolidated Balance Sheets was approximately $3 million and $1 million, respectively. Restricted cash was included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period amounts shown in the Company’s Condensed Consolidated Statements of Cash Flows for the nine months ended December 31, 2017 and 2016.
New Accounting Pronouncements	New Accounting Pronouncements: New Accounting Pronouncements Recently Adopted In March 2016, the FASB issued Accounting Standards Update No. 2016-09 (ASU 2016-09), Improvements to Employee Share-Based Payment Accounting (Topic 718), which is intended to simplify several aspects of the accounting for share-based payment award transactions, including the income tax consequences and classification on the statements of cash flows. ASU 2016-09 was adopted by the Company when effective in the first quarter of fiscal year 2018. The adoption of ASU 2016-09 resulted in the presentation of cash flows for employee taxes paid by withholding shares of restricted stock as a financing activity within the Condensed Consolidated Statements of Cash Flows, which were previously presented as an operating activity. A retrospective method of adoption was required for this change, which resulted in the reclassification of cash outflows of approximately $34 million from operating activities to financing activities within the Condensed Consolidated Statements of Cash Flows for the nine months ended December 31, 2016. Although not material, ASU 2016-09 also requires that excess tax benefits on share-based compensation expense be recognized in the Condensed Consolidated Statements of Operations as a component of the provision for income taxes, rather than additional paid-in capital, on a prospective basis. As permitted by ASU 2016-09, although not material, the Company elected to retrospectively reclassify cash flows related to excess tax benefits on share-based compensation expense as an operating activity within the Condensed Consolidated Statements of Cash Flows, which were previously presented as a financing activity. In addition, as permitted by ASU 2016-09, the Company elected to continue to estimate forfeitures expected to occur to determine the amount of share-based compensation expense to be recognized in each period. In August 2016, the FASB issued Accounting Standards Update No. 2016-15 (ASU 2016-15), Classification of Certain Cash Receipts and Cash Payments (Topic 230), which is intended to reduce diversity in practice on how certain cash receipts and cash payments are classified and presented in the statements of cash flows. In November 2016, the FASB issued Accounting Standards Update No. 2016-18 (ASU 2016-18), Restricted Cash (Topic 230), which is intended to reduce diversity in practice on how changes in restricted cash are classified and presented in the statements of cash flows. ASU 2016-18 requires amounts generally described as restricted cash to be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statements of cash flows. The Company elected to early adopt both ASU 2016-15 and ASU 2016-18 in the first quarter of fiscal year 2018 using the retrospective transition method of adoption. The adoption of these standards did not have a material effect on the Company’s consolidated financial statements and related disclosures. New Accounting Pronouncements Not Yet Adopted In May 2014, the FASB issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers, with amendments in 2015, 2016 and 2017, which creates new ASC Topic 606 (Topic 606) that will replace most existing revenue recognition guidance in GAAP when it becomes effective. Topic 606 requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. The new standard will be effective for the Company’s first quarter of fiscal year 2019 and early application for fiscal year 2018 is permitted. Topic 606 may be applied retrospectively to each prior period presented (full retrospective method) or with the cumulative effect recognized as of the date of initial application (modified retrospective method). The Company has established a cross-functional implementation team consisting of representatives across the organization and a third-party service provider to develop a project plan, including the evaluation of customer contracts across the organization, the development of policies, processes and tools to report financial results, the consideration of new performance measurements, and the implementation and evaluation of the Company’s internal controls over financial reporting that will be necessary under the new standard. The Company currently plans to adopt Topic 606 in the first quarter of fiscal year 2019 using the modified retrospective method. While the Company is continuing to determine the full effect of the new standard, it currently anticipates that this standard will have a material effect on its consolidated financial statements and related disclosures, and currently believes the most significant effect relates to the timing of the recognition of its software license revenue. Specifically, under the new standard, the Company currently expects to recognize license revenue for its Mainframe Solutions and Enterprise Solutions products at the point-in-time the licensed software is transferred to the customer, rather than ratably over the term of the customer contract as required by existing GAAP for most of the Company’s software arrangements. As a result, a significant portion of the Company’s revenue backlog (i.e., deferred revenue and future billings on committed contracts) relating to the license component of customer contracts at March 31, 2018 under existing GAAP will not be recognized as revenue in future periods but instead will be included as part of the cumulative effect adjustment within retained earnings upon adoption of Topic 606. Such cumulative effect adjustment will primarily result from (i) the significant reduction in deferred revenue relating to the license component of customer contracts as mentioned above, (ii) the establishment of a significant contract asset related to the Company’s contractual right to consideration for completed performance obligations not yet billed or collected (i.e., license revenue recognized in advance of billings), (iii) the increase in deferred tax liabilities arising from the increase in contract assets, and (iv) the increase in income taxes payable from both the increase in contract assets as a result of the Tax Cuts and Jobs Act enacted on December 22, 2017 (the “Tax Act”) and the portion of deferred revenue included in the cumulative effect adjustment that has not been previously included as taxable income on a tax return. The increase in contract assets and decrease in deferred revenue, when taken together with those provisions of the Tax Act which affect tax method revenue recognition for accrual-method U.S. taxpayers, will result in an acceleration of the timing of the Company’s income tax payments. This acceleration of the timing of income tax payments will be significant in relation to the Company’s current annual income tax payments within cash flows from operations. While the Company has not finalized its assessment of the impact arising from the Topic 606 adoption and finalization of the assessment could result in revisions to these estimates, which could be material, the Company currently estimates additional income tax payments in the range of approximately $100 million to $150 million per year over a four-year period, beginning in fiscal year 2019. The Company currently expects these additional income tax payments will be largely offset by the benefit from the reduced U.S. corporate tax rate enacted by the Tax Act. The Company believes that taken together, the incremental income tax payments resulting from the Topic 606 adoption and enactment of the Tax Act will be approximately $25 million to $50 million, on average, per year for the next four years, beginning in fiscal year 2019. Although the Company continues to evaluate the items listed above, it does not currently expect Topic 606 to have a significant effect on its customer billings and cash collections from customer billings. The Company currently believes that the point-in-time recognition requirement of the new standard will increase the variability of its revenue and overall net income period-to-period. The Company does not currently expect Topic 606 will have a significant effect on the timing of revenue recognition for its maintenance, Software-as-a-Service and professional services contracts. However, under Topic 606, more judgment and estimates will be required within the revenue recognition process than are required under existing GAAP, including estimates of the standalone selling price for each performance obligation identified within the Company’s contracts. These judgments and estimates will also impact the proportion of a contract’s value that is reported as license, maintenance and other elements, and the amounts assigned to the Company’s reportable segments. Topic 606 will also require the Company to capitalize a portion of its sales commissions and other incremental costs to acquire contracts (i.e., contract costs), which are currently expensed as incurred. Upon adoption of Topic 606, the capitalization of contract costs will be included as part of the cumulative effect adjustment within retained earnings. The Company currently anticipates it will amortize these capitalized contract costs over an expected period of benefit ranging from approximately four to seven years. The Company is currently evaluating the effect of this requirement on its consolidated financial statements and related disclosures. In February 2016, the FASB issued Accounting Standards Update No. 2016-02 (ASU 2016-02), Leases (Topic 842), which requires a lessee to recognize assets and liabilities on its consolidated balance sheet for leases with accounting lease terms of more than 12 months. ASU 2016-02 will replace most existing lease accounting guidance in GAAP when it becomes effective. The new standard states that a lessee will recognize a lease liability for the obligation to make lease payments and a right-of-use asset for the right to use the underlying asset for the lease term. Leases will be classified as either finance or operating, with classification affecting the pattern of expense recognition in the consolidated statements of operations. ASU 2016-02 will be effective for the Company’s first quarter of fiscal year 2020 and requires the modified retrospective method of adoption. Early adoption is permitted. Although the Company is currently evaluating the timing of adoption and the effect that ASU 2016-02 will have on its consolidated financial statements and related disclosures, the Company currently expects that most of its operating lease commitments will be subject to the new standard and recognized as operating lease liabilities and right-of-use assets upon adoption. In October 2016, the FASB issued Accounting Standards Update No. 2016-16 (ASU 2016-16), Intra-Equity Transfers of Assets Other Than Inventory (Topic 740), which is intended to eliminate diversity in practice and provide a more accurate depiction of the tax consequences on intercompany asset transfers (excluding inventory). ASU 2016-16 requires entities to immediately recognize the tax consequences on intercompany asset transfers (excluding inventory) at the transaction date, rather than deferring the tax consequences under current GAAP. ASU 2016-16 will be effective for the Company’s first quarter of fiscal year 2019 and requires a modified retrospective method of adoption. Early adoption is permitted, but only in the first quarter of an entity’s fiscal year. The Company does not currently expect the adoption of ASU 2016-16 to have a material effect on its consolidated financial statements and related disclosures. In January 2017, the FASB issued Accounting Standards Update No. 2017-04 (ASU 2017-04), Simplifying the Test for Goodwill Impairment (Topic 350), which is intended to simplify the subsequent measurement of goodwill. ASU 2017-04 eliminates Step 2 of the goodwill impairment test requiring the assessment of fair value of individual assets and liabilities of a reporting unit to measure goodwill impairments. Upon adoption of this new standard, goodwill impairments will be the amount by which a reporting unit's carrying value exceeds its fair value. ASU 2017-04 will be effective for the Company’s first quarter of fiscal year 2021 and requires a prospective method of adoption. Early adoption is permitted. The Company is currently evaluating the timing of adoption and the effect that ASU 2017-04 will have on its consolidated financial statements and related disclosures. In August 2017, the FASB issued Accounting Standards Update No. 2017-12 (ASU 2017-12), Targeted Improvements to Accounting for Hedging Activities (Topic 815), which is intended to improve the financial reporting of hedging relationships to better portray the economic results of risk management activities in financial statements. ASU 2017-12 makes certain targeted improvements to simplify the application of the hedge accounting guidance in current GAAP. ASU 2017-12 will be effective for the Company’s first quarter of fiscal year 2020 and requires a prospective method of adoption for the amended presentation and disclosure guidance. Early adoption is permitted. The Company is currently evaluating the timing of adoption and the effect that ASU 2017-12 will have on its consolidated financial statements and related disclosures.

New Accounting Pronouncements:

New Accounting Pronouncements Recently Adopted

In March 2016, the FASB issued Accounting Standards Update No. 2016-09 (ASU 2016-09), Improvements to Employee Share-Based Payment Accounting (Topic 718), which is intended to simplify several aspects of the accounting for share-based payment award transactions, including the income tax consequences and classification on the statements of cash flows. ASU 2016-09 was adopted by the Company when effective in the first quarter of fiscal year 2018. The adoption of ASU 2016-09 resulted in the presentation of cash flows for employee taxes paid by withholding shares of restricted stock as a financing activity within the Condensed Consolidated Statements of Cash Flows, which were previously presented as an operating activity. A retrospective method of adoption was required for this change, which resulted in the reclassification of cash outflows of approximately $34 million from operating activities to financing activities within the Condensed Consolidated Statements of Cash Flows for the nine months ended December 31, 2016. Although not material, ASU 2016-09 also requires that excess tax benefits on share-based compensation expense be recognized in the Condensed Consolidated Statements of Operations as a component of the provision for income taxes, rather than additional paid-in capital, on a prospective basis. As permitted by ASU 2016-09, although not material, the Company elected to retrospectively reclassify cash flows related to excess tax benefits on share-based compensation expense as an operating activity within the Condensed Consolidated Statements of Cash Flows, which were previously presented as a financing activity. In addition, as permitted by ASU 2016-09, the Company elected to continue to estimate forfeitures expected to occur to determine the amount of share-based compensation expense to be recognized in each period.

In August 2016, the FASB issued Accounting Standards Update No. 2016-15 (ASU 2016-15), Classification of Certain Cash Receipts and Cash Payments (Topic 230), which is intended to reduce diversity in practice on how certain cash receipts and cash payments are classified and presented in the statements of cash flows. In November 2016, the FASB issued Accounting Standards Update No. 2016-18 (ASU 2016-18), Restricted Cash (Topic 230), which is intended to reduce diversity in practice on how changes in restricted cash are classified and presented in the statements of cash flows. ASU 2016-18 requires amounts generally described as restricted cash to be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statements of cash flows. The Company elected to early adopt both ASU 2016-15 and ASU 2016-18 in the first quarter of fiscal year 2018 using the retrospective transition method of adoption. The adoption of these standards did not have a material effect on the Company’s consolidated financial statements and related disclosures.

New Accounting Pronouncements Not Yet Adopted

In May 2014, the FASB issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers, with amendments in 2015, 2016 and 2017, which creates new ASC Topic 606 (Topic 606) that will replace most existing revenue recognition guidance in GAAP when it becomes effective. Topic 606 requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. The new standard will be effective for the Company’s first quarter of fiscal year 2019 and early application for fiscal year 2018 is permitted. Topic 606 may be applied retrospectively to each prior period presented (full retrospective method) or with the cumulative effect recognized as of the date of initial application (modified retrospective method).

The Company has established a cross-functional implementation team consisting of representatives across the organization and a third-party service provider to develop a project plan, including the evaluation of customer contracts across the organization, the development of policies, processes and tools to report financial results, the consideration of new performance measurements, and the implementation and evaluation of the Company’s internal controls over financial reporting that will be necessary under the new standard. The Company currently plans to adopt Topic 606 in the first quarter of fiscal year 2019 using the modified retrospective method.

While the Company is continuing to determine the full effect of the new standard, it currently anticipates that this standard will have a material effect on its consolidated financial statements and related disclosures, and currently believes the most significant effect relates to the timing of the recognition of its software license revenue. Specifically, under the new standard, the Company currently expects to recognize license revenue for its Mainframe Solutions and Enterprise Solutions products at the point-in-time the licensed software is transferred to the customer, rather than ratably over the term of the customer contract as required by existing GAAP for most of the Company’s software arrangements. As a result, a significant portion of the Company’s revenue backlog (i.e., deferred revenue and future billings on committed contracts) relating to the license component of customer contracts at March 31, 2018 under existing GAAP will not be recognized as revenue in future periods but instead will be included as part of the cumulative effect adjustment within retained earnings upon adoption of Topic 606. Such cumulative effect adjustment will primarily result from (i) the significant reduction in deferred revenue relating to the license component of customer contracts as mentioned above, (ii) the establishment of a significant contract asset related to the Company’s contractual right to consideration for completed performance obligations not yet billed or collected (i.e., license revenue recognized in advance of billings), (iii) the increase in deferred tax liabilities arising from the increase in contract assets, and (iv) the increase in income taxes payable from both the increase in contract assets as a result of the Tax Cuts and Jobs Act enacted on December 22, 2017 (the “Tax Act”) and the portion of deferred revenue included in the cumulative effect adjustment that has not been previously included as taxable income on a tax return. The increase in contract assets and decrease in deferred revenue, when taken together with those provisions of the Tax Act which affect tax method revenue recognition for accrual-method U.S. taxpayers, will result in an acceleration of the timing of the Company’s income tax payments. This acceleration of the timing of income tax payments will be significant in relation to the Company’s current annual income tax payments within cash flows from operations. While the Company has not finalized its assessment of the impact arising from the Topic 606 adoption and finalization of the assessment could result in revisions to these estimates, which could be material, the Company currently estimates additional income tax payments in the range of approximately $100 million to $150 million per year over a four-year period, beginning in fiscal year 2019. The Company currently expects these additional income tax payments will be largely offset by the benefit from the reduced U.S. corporate tax rate enacted by the Tax Act. The Company believes that taken together, the incremental income tax payments resulting from the Topic 606 adoption and enactment of the Tax Act will be approximately $25 million to $50 million, on average, per year for the next four years, beginning in fiscal year 2019. Although the Company continues to evaluate the items listed above, it does not currently expect Topic 606 to have a significant effect on its customer billings and cash collections from customer billings.

The Company currently believes that the point-in-time recognition requirement of the new standard will increase the variability of its revenue and overall net income period-to-period. The Company does not currently expect Topic 606 will have a significant effect on the timing of revenue recognition for its maintenance, Software-as-a-Service and professional services contracts. However, under Topic 606, more judgment and estimates will be required within the revenue recognition process than are required under existing GAAP, including estimates of the standalone selling price for each performance obligation identified within the Company’s contracts. These judgments and estimates will also impact the proportion of a contract’s value that is reported as license, maintenance and other elements, and the amounts assigned to the Company’s reportable segments.

Topic 606 will also require the Company to capitalize a portion of its sales commissions and other incremental costs to acquire contracts (i.e., contract costs), which are currently expensed as incurred. Upon adoption of Topic 606, the capitalization of contract costs will be included as part of the cumulative effect adjustment within retained earnings. The Company currently anticipates it will amortize these capitalized contract costs over an expected period of benefit ranging from approximately four to seven years. The Company is currently evaluating the effect of this requirement on its consolidated financial statements and related disclosures.

In February 2016, the FASB issued Accounting Standards Update No. 2016-02 (ASU 2016-02), Leases (Topic 842), which requires a lessee to recognize assets and liabilities on its consolidated balance sheet for leases with accounting lease terms of more than 12 months. ASU 2016-02 will replace most existing lease accounting guidance in GAAP when it becomes effective. The new standard states that a lessee will recognize a lease liability for the obligation to make lease payments and a right-of-use asset for the right to use the underlying asset for the lease term. Leases will be classified as either finance or operating, with classification affecting the pattern of expense recognition in the consolidated statements of operations. ASU 2016-02 will be effective for the Company’s first quarter of fiscal year 2020 and requires the modified retrospective method of adoption. Early adoption is permitted. Although the Company is currently evaluating the timing of adoption and the effect that ASU 2016-02 will have on its consolidated financial statements and related disclosures, the Company currently expects that most of its operating lease commitments will be subject to the new standard and recognized as operating lease liabilities and right-of-use assets upon adoption.

In October 2016, the FASB issued Accounting Standards Update No. 2016-16 (ASU 2016-16), Intra-Equity Transfers of Assets Other Than Inventory (Topic 740), which is intended to eliminate diversity in practice and provide a more accurate depiction of the tax consequences on intercompany asset transfers (excluding inventory). ASU 2016-16 requires entities to immediately recognize the tax consequences on intercompany asset transfers (excluding inventory) at the transaction date, rather than deferring the tax consequences under current GAAP. ASU 2016-16 will be effective for the Company’s first quarter of fiscal year 2019 and requires a modified retrospective method of adoption. Early adoption is permitted, but only in the first quarter of an entity’s fiscal year. The Company does not currently expect the adoption of ASU 2016-16 to have a material effect on its consolidated financial statements and related disclosures.

In January 2017, the FASB issued Accounting Standards Update No. 2017-04 (ASU 2017-04), Simplifying the Test for Goodwill Impairment (Topic 350), which is intended to simplify the subsequent measurement of goodwill. ASU 2017-04 eliminates Step 2 of the goodwill impairment test requiring the assessment of fair value of individual assets and liabilities of a reporting unit to measure goodwill impairments. Upon adoption of this new standard, goodwill impairments will be the amount by which a reporting unit's carrying value exceeds its fair value. ASU 2017-04 will be effective for the Company’s first quarter of fiscal year 2021 and requires a prospective method of adoption. Early adoption is permitted. The Company is currently evaluating the timing of adoption and the effect that ASU 2017-04 will have on its consolidated financial statements and related disclosures.

In August 2017, the FASB issued Accounting Standards Update No. 2017-12 (ASU 2017-12), Targeted Improvements to Accounting for Hedging Activities (Topic 815), which is intended to improve the financial reporting of hedging relationships to better portray the economic results of risk management activities in financial statements. ASU 2017-12 makes certain targeted improvements to simplify the application of the hedge accounting guidance in current GAAP. ASU 2017-12 will be effective for the Company’s first quarter of fiscal year 2020 and requires a prospective method of adoption for the amended presentation and disclosure guidance. Early adoption is permitted. The Company is currently evaluating the timing of adoption and the effect that ASU 2017-12 will have on its consolidated financial statements and related disclosures.