Subsequent Events (Notes)	9 Months Ended
Sep. 30, 2016
Subsequent Events [Abstract]
Mergers, Acquisitions and Dispositions Disclosures [Text Block]	CenturyLink Merger On October 31, 2016, the Company entered into an agreement and plan of merger (the "Merger Agreement") with CenturyLink, Inc. ("CenturyLink"), Wildcat Merger Sub 1 LLC, a Delaware limited liability company and an indirect wholly-owned subsidiary of CenturyLink ("Merger Sub 1"), and WWG Merger Sub LLC, a Delaware limited liability company and an indirect wholly-owned subsidiary of CenturyLink ("Merger Sub 2"), pursuant to which, subject to the satisfaction or waiver of the conditions set forth in the Merger Agreement, the Company will be acquired by CenturyLink in a cash and stock transaction, including the assumption of the Company's debt (the "CenturyLink Merger"). Under the Merger Agreement, at the effective time of the merger of Merger Sub 1 with and into the Company (the "Initial Merger"), (i) each issued and outstanding share of common stock of the Company, will be converted into 1.4286 shares (the "Stock Consideration") of CenturyLink's common stock par value $1.00 per share and (ii) the right to receive $26.50 in cash (the "Cash Consideration" and, together with the Stock Consideration, the "Merger Consideration"). In addition, the Merger Agreement provides that at the effective time of the CenturyLink Merger, each issued and outstanding restricted stock unit award granted prior to April 1, 2014 and each restricted stock unit award granted to a non-employee member of the Company’s Board of Directors will be exchanged for the Merger Consideration. Further, at the effective time of the CenturyLink Merger, each issued and outstanding restricted stock unit award granted on or after April 1, 2014, other than those granted to non-employee members of the Company’s Board of Directors, will be assumed and converted automatically into a restricted stock unit award of CenturyLink common stock that will be subject to the same service-based vesting conditions as applicable to such awards prior to the transaction (but not any performance-based vesting conditions, which will be deemed satisfied based on forecasted and adjusted results through the closing of the transaction (as determined by Compensation Committee of the Company’s Board of Directors)). The CenturyLink Merger is subject to the receipt of certain regulatory approvals, including expiration or termination of the applicable waiting period under the Hart-Scott-Rodino Antitrust Improvements Act, review by the U.S. Federal Communications Commission, certain state regulatory approvals and other customary closing conditions. The transaction is also subject to the approval of CenturyLink shareholders and Level 3 stockholders. CenturyLink has entered into a voting agreement with STT Crossing Ltd. (a wholly owned subsidiary of ST Telemedia), holder of approximately 18 percent of Level 3's outstanding common stock, pursuant to which it will vote its Level 3 shares in favor of the transaction. All existing indebtedness of Level 3 is expected to remain in place at Level 3 and Level 3 will not incur any incremental indebtedness or guarantee any indebtedness of CenturyLink to finance the transaction.

CenturyLink Merger

On October 31, 2016, the Company entered into an agreement and plan of merger (the "Merger Agreement") with CenturyLink, Inc. ("CenturyLink"), Wildcat Merger Sub 1 LLC, a Delaware limited liability company and an indirect wholly-owned subsidiary of CenturyLink ("Merger Sub 1"), and WWG Merger Sub LLC, a Delaware limited liability company and an indirect wholly-owned subsidiary of CenturyLink ("Merger Sub 2"), pursuant to which, subject to the satisfaction or waiver of the conditions set forth in the Merger Agreement, the Company will be acquired by CenturyLink in a cash and stock transaction, including the assumption of the Company's debt (the "CenturyLink Merger").

Under the Merger Agreement, at the effective time of the merger of Merger Sub 1 with and into the Company (the "Initial Merger"), (i) each issued and outstanding share of common stock of the Company, will be converted into 1.4286 shares (the "Stock Consideration") of CenturyLink's common stock par value $1.00 per share and (ii) the right to receive $26.50 in cash (the "Cash Consideration" and, together with the Stock Consideration, the "Merger Consideration"). In addition, the Merger Agreement provides that at the effective time of the CenturyLink Merger, each issued and outstanding restricted stock unit award granted prior to April 1, 2014 and each restricted stock unit award granted to a non-employee member of the Company’s Board of Directors will be exchanged for the Merger Consideration. Further, at the effective time of the CenturyLink Merger, each issued and outstanding restricted stock unit award granted on or after April 1, 2014, other than those granted to non-employee members of the Company’s Board of Directors, will be assumed and converted automatically into a restricted stock unit award of CenturyLink common stock that will be subject to the same service-based vesting conditions as applicable to such awards prior to the transaction (but not any performance-based vesting conditions, which will be deemed satisfied based on forecasted and adjusted results through the closing of the transaction (as determined by Compensation Committee of the Company’s Board of Directors)). The CenturyLink Merger is subject to the receipt of certain regulatory approvals, including expiration or termination of the applicable waiting period under the Hart-Scott-Rodino Antitrust Improvements Act, review by the U.S. Federal Communications Commission, certain state regulatory approvals and other customary closing conditions. The transaction is also subject to the approval of CenturyLink shareholders and Level 3 stockholders. CenturyLink has entered into a voting agreement with STT Crossing Ltd. (a wholly owned subsidiary of ST Telemedia), holder of approximately 18 percent of Level 3's outstanding common stock, pursuant to which it will vote its Level 3 shares in favor of the transaction. All existing indebtedness of Level 3 is expected to remain in place at Level 3 and Level 3 will not incur any incremental indebtedness or guarantee any indebtedness of CenturyLink to finance the transaction.