Summary of Significant Accounting Policies (Policies)	9 Months Ended
Sep. 30, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Principles of Consolidation	Principles of Consolidation and Reporting These unaudited condensed consolidated financial statements include the accounts of Northrop Grumman Corporation and subsidiaries (herein referred to as “Northrop Grumman,” the “company,” “we,” “us,” or “our”). Material intercompany accounts, transactions and profits are eliminated in consolidation. Investments in equity securities and joint ventures where the company has significant influence, but not control, are accounted for using the equity method.
Basis of Presentation	The accompanying unaudited condensed consolidated financial statements are prepared in accordance with the rules of the Securities and Exchange Commission (SEC) for interim reporting. These financial statements include adjustments of a normal recurring nature considered necessary by management for a fair presentation of the company’s unaudited condensed consolidated financial position, results of operations and cash flows. The results reported in these unaudited condensed consolidated financial statements are not necessarily indicative of results that may be expected for the entire year. These unaudited condensed consolidated financial statements should be read in conjunction with the information contained in the company’s Annual Report on Form 10-K for the year ended December 31, 2015 (2015 Annual Report on Form 10-K) and the Form 8-K that we filed with the SEC on April 27, 2016, which recasts the disclosures in certain portions of the 2015 Annual Report on Form 10-K to reflect changes in the company’s organizational structure and reportable segments.
Fiscal Period Policy	The quarterly information is labeled using a calendar convention; that is, first quarter is consistently labeled as ending on March 31, second quarter as ending on June 30 and third quarter as ending on September 30. It is the company’s long-standing practice to establish actual interim closing dates using a “fiscal” calendar, in which we close our books on a Friday near these quarter-end dates in order to normalize the potentially disruptive effects of quarterly closings on business processes. This practice is only used at interim periods within a reporting year.
Accounting Estimates	Accounting Estimates The accompanying unaudited condensed consolidated financial statements are prepared in conformity with accounting principles generally accepted in the United States of America (GAAP). The preparation thereof requires management to make estimates and judgments that affect the reported amounts of assets and liabilities and the disclosure of contingencies at the date of the financial statements, as well as the reported amounts of sales and expenses during the reporting period. Estimates have been prepared using the most current and best available information; however, actual results could differ materially from those estimates.
Revenue Recognition	Contract sales may include estimated amounts not contractually agreed to by the customer, including cost or performance incentives (such as award and incentive fees), un-priced change orders, contract claims and requests for equitable adjustment (REAs). Further, as contracts are performed, change orders can be a regular occurrence and may be un-priced until negotiated with the customer. Un-priced change orders, contract claims (including change orders unapproved as to both scope and price) and REAs are included in estimated contract sales when management believes it is probable the un-priced change order, claim and/or REA will result in additional contract revenue and the amount can be reliably estimated based on the facts and circumstances known to us at the time. The majority of our sales are derived from long-term contracts with the United States (U.S.) Government for the production of goods, the provision of services, or in some cases, a combination of both. In accounting for these contracts, we utilize either the cost-to-cost method or the units-of-delivery method of percentage-of-completion accounting, with cost-to-cost being the predominant method. The company estimates profit on contracts as the difference between total estimated sales and total estimated cost at completion and recognizes that profit either as costs are incurred (cost-to-cost) or as units are delivered (units-of-delivery). The company classifies sales as product or service depending upon the predominant attributes of the contract. Net Estimate-At-Completion (EAC) Adjustments - We recognize changes in estimated contract sales, costs or profits using the cumulative catch-up method of accounting. This method recognizes, in the current period, the cumulative effect of the changes on current and prior periods as net EAC adjustments; sales and profit in future periods of contract performance are recognized as if the revised estimates had been used since contract inception. If it is determined that a loss will result from the performance of a contract, the entire amount of the estimable future loss is charged against income in the period the loss is identified. Loss provisions are first offset against costs included in unbilled accounts receivable or inventoried costs, and any remaining amounts are reflected in current liabilities. Significant EAC adjustments on a single contract could have a material effect on the company’s unaudited condensed consolidated financial position or results of operations. When such adjustments occur, we generally disclose the nature, underlying conditions and financial impact of the adjustments.
Description of New Accounting Pronouncements Not yet Adopted	On February 25, 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). ASU 2016-02 supersedes existing lease guidance, including Accounting Standards Codification (ASC) 840 - Leases. Among other things, ASU 2016-02 requires recognition of a right-of-use asset and liability for future lease payments for contracts that meet the definition of a lease. ASU 2016-02 will be effective January 1, 2019, although early adoption is permitted, and it must be applied using a modified retrospective approach. We are currently evaluating the timing of adoption as well as the effect ASU 2016-02 will have on the company’s consolidated financial position, annual results of operations and/or cash flows. On May 28, 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers. ASU 2014-09 supersedes existing revenue recognition guidance, including ASC 605-35, Revenue Recognition - Construction-Type and Production-Type Contracts. ASU 2014-09 outlines a single set of comprehensive principles for recognizing revenue under U.S. GAAP. Among other things, it requires companies to identify contractual performance obligations and determine whether revenue should be recognized at a point in time or over time. These concepts, as well as other aspects of ASU 2014-09, may change the method and/or timing of revenue recognition for certain of our contracts. We expect to adopt ASU 2014-09 in 2018 and apply it retrospectively to all periods presented. Our evaluation of the effect ASU 2014-09 will have on the company’s consolidated financial position, annual results of operations and/or cash flows is expected to be complete by the end of 2016.
Stockholders' Equity	The company records the difference between the cost of shares repurchased and their par value as well as tax withholding in excess of related stock compensation expense as a reduction of paid-in capital to the extent available and then as a reduction of retained earnings.
Pension and Other Postretirement Plans	Net actuarial gains or losses are re-determined annually or upon remeasurement events and principally arise from changes in the interest rate used to discount our benefit obligations and differences between expected and actual returns on plan assets. We fund our defined benefit pension plans annually in a manner consistent with the Employee Retirement Income Security Act of 1974, as amended by the Pension Protection Act of 2006.
Earnings Per Share	We calculate basic earnings per share by dividing net earnings by the weighted-average number of shares of common stock outstanding during each period. Diluted earnings per share includes the dilutive effect of awards granted to employees under stock-based compensation plans.
Investments in Marketable Securities	Investments in Marketable Securities The company holds a portfolio of marketable securities consisting of securities to partially fund non-qualified employee benefit plans. These assets are recorded at fair value on a recurring basis and substantially all of these instruments are valued using Level 1 inputs.
Derivative Financial Instruments and Hedging Activities	Substantially all of these instruments are valued using Level 2 inputs. Where model-derived valuations are appropriate, the company utilizes the income approach to determine the fair value and uses the applicable London Interbank Offered Rate (LIBOR) swap rates.
Fair Value of Long-term Debt	The fair value of long-term debt is calculated using Level 2 inputs based on interest rates available for debt with terms and maturities similar to the company’s existing debt arrangements.
Guarantees of Certain Performance Obligations	Guarantees of Certain Performance Obligations The company’s subsidiaries enter into joint ventures, teaming and other business arrangements (collectively, Business Arrangements) to support our products and services. The company generally strives to limit its exposure under these arrangements to its subsidiary’s investment in the Business Arrangements or to the extent of such subsidiary’s obligations under the applicable contract. In some cases, however, the company may be required to guarantee performance by the Business Arrangements and, in such cases, the company generally strives to obtain cross-indemnification from the other members of the Business Arrangements.
U.S. Government Cost Claims	U.S. Government Cost Claims From time to time, the company is advised of claims by the U.S. Government concerning certain potential disallowed costs, plus, at times, penalties and interest. When such findings are presented, the company and the U.S. Government representatives engage in discussions to enable the company to evaluate the merits of these claims, as well as to assess the amounts being claimed. Where appropriate, provisions are made to reflect the company’s estimated exposure for matters raised by the U.S. Government. Such provisions are reviewed periodically using the most recent information available.
Environmental Matters	These amounts are evaluated for recoverability on a routine basis.
New Accounting Pronouncements and Changes in Accounting Principles [Text Block]	On March 30, 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting. The company adopted ASU 2016-09 during the first quarter of 2016. Among other things, ASU 2016-09 requires that entities recognize excess tax benefits and deficiencies related to employee share-based payment transactions as income tax expense or benefit. ASU 2016-09 also eliminates the requirement to reclassify excess tax benefits and deficiencies from operating activities to financing activities in the statement of cash flows. As a result of adoption, the company recognized a $1 million and $85 million tax benefit during the three and nine months ended September 30, 2016, respectively. Adoption also resulted in an $85 million increase in operating cash flows and a corresponding $85 million reduction in financing cash flows for the nine months ended September 30, 2016. The company adopted ASU 2015-03, Interest - Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs, during the first quarter of 2016. As a result, we now present capitalized debt issuance costs as a reduction in the carrying amount of long-term debt. This change resulted in a reclassification of $30 million of other non-current assets reported in our 2015 consolidated statement of financial position to long-term debt, which reduced our previously reported total assets and total liabilities as of December 31, 2015.

Summary of Significant Accounting Policies (Policies)

9 Months Ended

Sep. 30, 2016

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Principles of Consolidation and Reporting

These unaudited condensed consolidated financial statements include the accounts of Northrop Grumman Corporation and subsidiaries (herein referred to as “Northrop Grumman,” the “company,” “we,” “us,” or “our”). Material intercompany accounts, transactions and profits are eliminated in consolidation. Investments in equity securities and joint ventures where the company has significant influence, but not control, are accounted for using the equity method.

Basis of Presentation

The accompanying unaudited condensed consolidated financial statements are prepared in accordance with the rules of the Securities and Exchange Commission (SEC) for interim reporting. These financial statements include adjustments of a normal recurring nature considered necessary by management for a fair presentation of the company’s unaudited condensed consolidated financial position, results of operations and cash flows.

The results reported in these unaudited condensed consolidated financial statements are not necessarily indicative of results that may be expected for the entire year. These unaudited condensed consolidated financial statements should be read in conjunction with the information contained in the company’s Annual Report on Form 10-K for the year ended December 31, 2015 (2015 Annual Report on Form 10-K) and the Form 8-K that we filed with the SEC on April 27, 2016, which recasts the disclosures in certain portions of the 2015 Annual Report on Form 10-K to reflect changes in the company’s organizational structure and reportable segments.

Fiscal Period Policy

The quarterly information is labeled using a calendar convention; that is, first quarter is consistently labeled as ending on March 31, second quarter as ending on June 30 and third quarter as ending on September 30. It is the company’s long-standing practice to establish actual interim closing dates using a “fiscal” calendar, in which we close our books on a Friday near these quarter-end dates in order to normalize the potentially disruptive effects of quarterly closings on business processes. This practice is only used at interim periods within a reporting year.

Accounting Estimates

The accompanying unaudited condensed consolidated financial statements are prepared in conformity with accounting principles generally accepted in the United States of America (GAAP). The preparation thereof requires management to make estimates and judgments that affect the reported amounts of assets and liabilities and the disclosure of contingencies at the date of the financial statements, as well as the reported amounts of sales and expenses during the reporting period. Estimates have been prepared using the most current and best available information; however, actual results could differ materially from those estimates.

Revenue Recognition

Contract sales may include estimated amounts not contractually agreed to by the customer, including cost or performance incentives (such as award and incentive fees), un-priced change orders, contract claims and requests for equitable adjustment (REAs). Further, as contracts are performed, change orders can be a regular occurrence and may be un-priced until negotiated with the customer. Un-priced change orders, contract claims (including change orders unapproved as to both scope and price) and REAs are included in estimated contract sales when management believes it is probable the un-priced change order, claim and/or REA will result in additional contract revenue and the amount can be reliably estimated based on the facts and circumstances known to us at the time.

The majority of our sales are derived from long-term contracts with the United States (U.S.) Government for the production of goods, the provision of services, or in some cases, a combination of both. In accounting for these contracts, we utilize either the cost-to-cost method or the units-of-delivery method of percentage-of-completion accounting, with cost-to-cost being the predominant method. The company estimates profit on contracts as the difference between total estimated sales and total estimated cost at completion and recognizes that profit either as costs are incurred (cost-to-cost) or as units are delivered (units-of-delivery). The company classifies sales as product or service depending upon the predominant attributes of the contract.

Net Estimate-At-Completion (EAC) Adjustments - We recognize changes in estimated contract sales, costs or profits using the cumulative catch-up method of accounting. This method recognizes, in the current period, the cumulative effect of the changes on current and prior periods as net EAC adjustments; sales and profit in future periods of contract performance are recognized as if the revised estimates had been used since contract inception. If it is determined that a loss will result from the performance of a contract, the entire amount of the estimable future loss is charged against income in the period the loss is identified. Loss provisions are first offset against costs included in unbilled accounts receivable or inventoried costs, and any remaining amounts are reflected in current liabilities.

Significant EAC adjustments on a single contract could have a material effect on the company’s unaudited condensed consolidated financial position or results of operations. When such adjustments occur, we generally disclose the nature, underlying conditions and financial impact of the adjustments.

Description of New Accounting Pronouncements Not yet Adopted

On February 25, 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). ASU 2016-02 supersedes existing lease guidance, including Accounting Standards Codification (ASC) 840 - Leases. Among other things, ASU 2016-02 requires recognition of a right-of-use asset and liability for future lease payments for contracts that meet the definition of a lease. ASU 2016-02 will be effective January 1, 2019, although early adoption is permitted, and it must be applied using a modified retrospective approach. We are currently evaluating the timing of adoption as well as the effect ASU 2016-02 will have on the company’s consolidated financial position, annual results of operations and/or cash flows.

On May 28, 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers. ASU 2014-09 supersedes existing revenue recognition guidance, including ASC 605-35, Revenue Recognition - Construction-Type and Production-Type Contracts. ASU 2014-09 outlines a single set of comprehensive principles for recognizing revenue under U.S. GAAP. Among other things, it requires companies to identify contractual performance obligations and determine whether revenue should be recognized at a point in time or over time. These concepts, as well as other aspects of ASU 2014-09, may change the method and/or timing of revenue recognition for certain of our contracts. We expect to adopt ASU 2014-09 in 2018 and apply it retrospectively to all periods presented. Our evaluation of the effect ASU 2014-09 will have on the company’s consolidated financial position, annual results of operations and/or cash flows is expected to be complete by the end of 2016.

Stockholders' Equity

The company records the difference between the cost of shares repurchased and their par value as well as tax withholding in excess of related stock compensation expense as a reduction of paid-in capital to the extent available and then as a reduction of retained earnings.

Pension and Other Postretirement Plans

Net actuarial gains or losses are re-determined annually or upon remeasurement events and principally arise from changes in the interest rate used to discount our benefit obligations and differences between expected and actual returns on plan assets.

We fund our defined benefit pension plans annually in a manner consistent with the Employee Retirement Income Security Act of 1974, as amended by the Pension Protection Act of 2006.

Earnings Per Share

We calculate basic earnings per share by dividing net earnings by the weighted-average number of shares of common stock outstanding during each period.

Diluted earnings per share includes the dilutive effect of awards granted to employees under stock-based compensation plans.

Investments in Marketable Securities

The company holds a portfolio of marketable securities consisting of securities to partially fund non-qualified employee benefit plans. These assets are recorded at fair value on a recurring basis and substantially all of these instruments are valued using Level 1 inputs.

Derivative Financial Instruments and Hedging Activities

Substantially all of these instruments are valued using Level 2 inputs. Where model-derived valuations are appropriate, the company utilizes the income approach to determine the fair value and uses the applicable London Interbank Offered Rate (LIBOR) swap rates.

Fair Value of Long-term Debt

The fair value of long-term debt is calculated using Level 2 inputs based on interest rates available for debt with terms and maturities similar to the company’s existing debt arrangements.

Guarantees of Certain Performance Obligations

The company’s subsidiaries enter into joint ventures, teaming and other business arrangements (collectively, Business Arrangements) to support our products and services. The company generally strives to limit its exposure under these arrangements to its subsidiary’s investment in the Business Arrangements or to the extent of such subsidiary’s obligations under the applicable contract. In some cases, however, the company may be required to guarantee performance by the Business Arrangements and, in such cases, the company generally strives to obtain cross-indemnification from the other members of the Business Arrangements.

U.S. Government Cost Claims

From time to time, the company is advised of claims by the U.S. Government concerning certain potential disallowed costs, plus, at times, penalties and interest. When such findings are presented, the company and the U.S. Government representatives engage in discussions to enable the company to evaluate the merits of these claims, as well as to assess the amounts being claimed. Where appropriate, provisions are made to reflect the company’s estimated exposure for matters raised by the U.S. Government. Such provisions are reviewed periodically using the most recent information available.

Environmental Matters

These amounts are evaluated for recoverability on a routine basis.

New Accounting Pronouncements and Changes in Accounting Principles [Text Block]

On March 30, 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting. The company adopted ASU 2016-09 during the first quarter of 2016. Among other things, ASU 2016-09 requires that entities recognize excess tax benefits and deficiencies related to employee share-based payment transactions as income tax expense or benefit. ASU 2016-09 also eliminates the requirement to reclassify excess tax benefits and deficiencies from operating activities to financing activities in the statement of cash flows. As a result of adoption, the company recognized a $1 million and $85 million tax benefit during the three and nine months ended September 30, 2016, respectively. Adoption also resulted in an $85 million increase in operating cash flows and a corresponding $85 million reduction in financing cash flows for the nine months ended September 30, 2016.

The company adopted ASU 2015-03, Interest - Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs, during the first quarter of 2016. As a result, we now present capitalized debt issuance costs as a reduction in the carrying amount of long-term debt. This change resulted in a reclassification of $30 million of other non-current assets reported in our 2015 consolidated statement of financial position to long-term debt, which reduced our previously reported total assets and total liabilities as of December 31, 2015.