Summary Of Significant Accounting Policies (Policy)	12 Months Ended
Summary Of Significant Accounting Policies (Policy)	Dec. 30, 2011
Summary Of Significant Accounting Policies [Abstract]
Nature Of Business	Nature of Business We design, develop and support telecommunications networking products. We generate revenue principally through the sale of these products to communications service providers worldwide as both stand-alone network elements and as elements of integrated solutions. We also generate revenue by providing services to our customers.
Principles Of Consolidation	Principles of Consolidation Our consolidated financial statements include the accounts of Tellabs and its subsidiaries. We eliminate all intercompany accounts and transactions.
Use Of Estimates	Use of Estimates The preparation of the financial statements in conformity with GAAP requires us to make estimates and assumptions that affect amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates.
Cash Equivalents	Cash Equivalents We consider all highly liquid debt instruments purchased with original maturities of three months or less to be cash equivalents.
Fair Value Of Financial Instruments	Fair Value of Financial Instruments Our financial instruments consist of cash and cash equivalents, accounts receivable, accounts payable, marketable securities and derivatives. The carrying value of the cash and cash equivalents, accounts receivable and accounts payable are reasonable estimates of their fair value because of their short-term nature. We determine the fair value of marketable securities and derivatives based on observable inputs such as quoted prices in active markets, or other than quoted prices in active markets, that are observable either directly or indirectly. See discussion in Notes 7 and 8 regarding investments and derivatives, respectively.
Accounts Receivable Allowances	Accounts Receivable Allowances We base the reserve for allowances on an assessment of aged receivables and the collectability of customers' accounts. We regularly review the allowance by considering factors such as customer financial strength, the age of accounts receivable balances, current economic conditions that may affect a customer's ability to pay and historical experience. As specific balances are determined to be ultimately uncollectible, they are removed from accounts receivable.
Inventories And Suppliers	Inventories and Suppliers We determine inventory cost using the first-in, first-out method. We value inventory at the lower of cost or market, with market determined at the lower of current replacement cost or net realizable selling price. We determine the amount of inventory that is excess and obsolete and purchase commitments in excess of requirements using estimates of future demand for individual components of raw materials and finished goods. We outsource the manufacturing of products to third-party suppliers. Although a limited number of suppliers are used to manufacture our products, we believe other suppliers could provide similar products on comparable terms. An inability of a supplier to provide product could cause a near-term reduction of revenue, which would affect operating results adversely.
Property, Plant And Equipment	Property, Plant and Equipment We record property, plant and equipment at cost or fair value if acquired in a business combination, less accumulated depreciation and amortization. We compute depreciation using the straight-line method. Buildings are depreciated over 25 to 40 years; building improvements over 7 years; leasehold improvements over the lesser of the life of the lease or the useful life of the asset, currently 3 to 15 years; and equipment over 3 to 10 years. We evaluate property, plant and equipment for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset or asset group may not be fully recoverable.
Equity-Based Compensation	Equity-Based Compensation We recognize compensation expense for employee services received in exchange for awards of equity instruments based upon the grant date fair value of those awards over the requisite service period for the respective award.
Income Taxes	Income Taxes Deferred tax liabilities and assets are recognized for the expected future tax consequences of events that have been reflected in the consolidated financial statements. Deferred tax liabilities and assets are determined based on the differences between the book and tax bases of particular assets and liabilities as well as tax credit and operating loss carry forwards using tax rates in effect for the years in which the differences are expected to reverse. A valuation allowance is provided to offset deferred tax assets if, based upon the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized.
Goodwill	Goodwill Goodwill impairment is reviewed annually and when impairment indicators exist. Goodwill impairment reviews are conducted in two steps, the first of which is by comparing the segment's net book value to fair value. The process of evaluating the potential impairment of goodwill is subjective because it requires the use of estimates and assumptions. We calculate the fair value of the segment using a blended analysis of the discounted cash flow method and the market approach of valuation. The discounted cash flow method requires us to use estimates and judgments about the future cash flows of the segment. The assumptions used in our cash flow forecasts are consistent with plans and estimates we use to manage the underlying segment. The market approach requires us to make judgments to determine comparable publicly-traded companies. See the discussion in Note 5 regarding goodwill.
Intangible Assets	Intangible Assets Intangible assets are made up primarily of purchased technology and customer relationships from acquisitions. These assets are amortized over their estimated useful lives and reviewed for impairment when indicators of impairment exist, such as loss of customer relationships, customer nonacceptance of products and underlying technology, and reduced product margins indicating declining operating performance or cash flows. The estimated useful lives of these assets are evaluated to determine if a change in an estimate is required. The remaining carrying value of the asset is amortized prospectively over the remaining adjusted useful life of the asset. The review for potential impairment and change in estimated useful lives requires us to use estimates and judgments of future cash flows, consistent with plans and estimates we use to manage related product cash flows.
Revenue Recognition	Revenue Recognition Determining the proper revenue recognition in our financial statements requires us to make judgments about the application of the accounting rules based on the facts and circumstances of each customer arrangement. We recognize revenue when persuasive evidence of an arrangement exists, delivery has occurred or services have been rendered, the price or fee is fixed or determinable, and collectability is reasonably assured. Contracts and customer purchase orders are generally used to determine the existence of an arrangement. Shipping terms and related documents are used to verify delivery or performance. The Company assesses whether the sales price is fixed or determinable based on payment terms and whether the sales price is subject to refund or adjustment. If the price is not fixed or determinable, revenue is recognized as payments become due from the customer. Collectability is assessed based on the creditworthiness of the customer as determined by credit checks and the customer's payment history to the Company. If collectability is not considered probable, revenue is not recognized until the payment is made. The majority of revenue comes from product sales. We generally recognize revenue either upon shipment or upon delivery to the customer, depending on the contractual delivery terms. Some customer agreements contain acceptance clauses that grant the customer the right to return or exchange products that do not conform to specifications. If we do not have sufficient historical evidence of customer acceptance, we recognize revenue when we receive written evidence of customer acceptance or the acceptance provisions lapse. When we have sufficient historical evidence that products meet the specifications, we recognize revenue upon shipment or delivery provided title and risk of loss have transferred at that time. Some customer agreements grant the right to return or exchange product. We accrue for returns based on historical evidence of rates of return. We recognize revenue, net of potential returns, upon shipment or upon delivery of the product to the customer provided title and risk of loss have transferred at that time. Some customer arrangements are in the form of distribution agreements, with contractual rights of return, promotional rebates, and other incentives and credits allowances. We recognize revenue net of estimated returns and rebates, which are calculated based on contractual provisions and historical evidence of returns activity. We also recognize revenue from deployment services, support agreements, training and professional services. Deployment services revenue results from installation of products at customer sites. Installation services, which generally occur over a short time period, are not services required for the functionality of products, as customers do not have to purchase installation services from us, and may install products themselves, or hire third parties to perform the installation services. We recognize revenue for deployment services upon completion. We recognize revenue from support agreements ratably over the service period. We recognize training and professional services revenue upon completion. Many customer arrangements include the right to invoice the customer for costs of shipping product to the customer's location. In these cases, we record the amount included on the customer's invoice for shipping costs as revenue. The cost of shipping products to customers is recorded as cost of revenue. We record revenue net of any sales-related taxes that are imposed on a sale to our customers regardless of whether or not we bill the customer for such tax. We believe this approach results in financial statements that are more easily understood by investors. Accounting for multiple element arrangements entered into or materially modified after fiscal 2009 When a sales arrangement contains multiple deliverables, such as product sales that include services to be performed after delivery of the product, or where we sell multiple products to a customer, we account for a deliverable (or a group of deliverables) separately if (1) the delivered item(s) has stand-alone value to the customer, and (2) if we have given the customer a general right of return relative to the delivered item(s), delivery or performance of the undelivered item(s) or service(s) is probable and substantially in our control. Arrangement consideration is allocated to all deliverables based on the relative selling price using one of three methods: vendor – specific objective evidence, third-party evidence or estimated selling price. We use vendor-specific objective evidence if available, third-party evidence if vendor-specific objective evidence is not available or estimated selling price if neither vendor-specific objective evidence or third-party evidence is available. Revenue recognition for elements delivered will be limited to the amount that is not contingent on the future delivery of products and/or services, future performance obligations or subject to customer-specified return or refund privileges. We determine vendor-specific objective evidence of an item based on our selling price for a deliverable when sold on a stand-alone basis. Third-party evidence is determined based on a vendor's selling price for a comparable product or service on a stand-alone basis, if available. The best estimate of selling price is established based on internal factors including pricing practices, market conditions and product lifecycles. If we determine that the software products bundled with tangible products function together to deliver the product's essential functionality, we exclude them from the scope of software revenue recognition guidance. Accounting for multiple element arrangements entered into prior to fiscal 2010 For agreements with multiple-element arrangements entered into prior to 2010, we determine whether objective and reliable evidence of fair value for the items included in a multiple-element arrangement exist, based on whether we have vendor-specific objective evidence of the price that we sell an item for on a stand-alone basis. If we do not have vendor-specific objective evidence for the item, we use the price charged by a vendor selling a comparable product or service on a stand-alone basis to similarly situated customers, if available. When there is objective and reliable evidence of fair value for all units of accounting in an arrangement, we allocate the arrangement consideration to the separate units of accounting based on their relative fair values. In cases where we have objective and reliable evidence of fair value for the undelivered items in an arrangement, but no such evidence for the delivered items, we allocate the arrangement consideration using the residual method. If the elements are not considered separate units of accounting, or if we can't determine the fair value of any of the undelivered elements, we defer revenue until the entire arrangement is delivered or fair value is determined for all undelivered units of accounting. Once we determine the amount, if any, of arrangement consideration allocable to the undelivered item(s), we apply the applicable revenue recognition policy, as described elsewhere herein, to determine when such amount may be recognized as revenue. When an arrangement includes software that is more than incidental or the arrangement includes non-software elements for which software is essential to the functionality of the element, all elements of the arrangement are accounted for using software revenue recognition guidance.
Legal Costs	Legal Costs We expense legal costs associated with litigation defense as incurred.
Net Earnings (Loss) Per Share	Net Earnings per Share We base net earnings per share on the weighted average number of issued and outstanding common shares (basic) and the weighted average issued and outstanding common shares adjusted for assumed exercises of dilutive stock options, unvested restricted stock and unvested performance stock units (diluted). We base net earnings per share in periods of a net loss solely on basic weighted average number of common shares outstanding.
Foreign Currency Translations And Transactions	Foreign Currency Translation We generally measure the financial statements of foreign subsidiaries using the local currency as the functional currency. In such cases, we translate assets and liabilities at exchange rates in effect at the balance sheet date, and we translate revenue and expenses at weighted average exchange rates during the year. We record the gain or loss from translating a subsidiary's stockholders' equity into U.S. dollars as foreign currency translation adjustments in Accumulated other comprehensive income. Foreign Currency Transactions We recognize foreign currency transaction gains and losses resulting from changes in exchange rates due to the settlement of monetary assets and liabilities in a currency other than the subsidiary's functional currency in Other (expense) income, net.