Employee Benefits	12 Months Ended
Dec. 31, 2018
Retirement Benefits [Abstract]
Employee Benefits	Employee Benefits Defined Contribution Plans Prior to the CenturyLink acquisition on November 1, 2017, we offered our qualified employees the opportunity to participate in a defined contribution retirement plan qualifying under the provisions of Section 401(k) of the Internal Revenue Code ("401(k) Plan"). Each employee was eligible to contribute, on a tax deferred basis, a portion of annual earnings generally not to exceed $18,500 in 2018, $18,000 in 2017 and $18,000 in 2016. We matched 100% of employee contributions up to 4% of eligible earnings or applicable regulatory limits. Effective December 31, 2017, the Level 3 Communications, Inc. 401(k) Profit Sharing Plan and Trust assets merged with the CenturyLink, Inc. Dollars & Sense 401(k) Plan. Those employees eligible to contribute to the Level 3 Plan at December 31, 2017 were automatically enrolled in the CenturyLink Plan at January 1, 2018. Provisions regarding eligibility, participant and employer contributions, vesting, and benefit payments within the Level 3 Plan document did not materially change and protected provisions applicable to Level 3 and its predecessor Plans remained grandfathered as required by law. Prior to the CenturyLink acquisition on November 1, 2017, our matching contributions were made with Level 3 common stock based on the closing stock price on each pay date. After our acquisition, matching contributions were made in cash. We made 401(k) Plan matching contributions of $7 million for the successor period ended December 31, 2017, and $30 million and $37 million for the predecessor period ended October 31, 2017 and for the predecessor year ended December 31, 2016, respectively. Our matching contributions are recorded as compensation and included in cost of services of $1 million for the successor period ended December 31, 2017, and $4 million and $5 million for the predecessor period ended October 31, 2017 and for the predecessor year ended December 31, 2016, respectively. Our matching contributions included in selling, general and administrative expenses totaled $5 million for the successor period ended December 31, 2017, and $26 million and $32 million for the predecessor period ended October 31, 2017 and for the predecessor year ended December 31, 2016, respectively. Other defined contribution plans we sponsored are individually not significant. On an aggregate basis, the expense we recorded relating to these plans was approximately $5 million and $1 million for the successor year ended December 31, 2018 and period ended December 31, 2017, and $5 million and $6 million for the predecessor period ended October 31, 2017 and for the predecessor year ended December 31, 2016, respectively. Defined Benefit Plans We have certain contributory and non-contributory employee pension plans, which are not significant to our financial position or operating results. We recognize in our balance sheet the funded status of our defined benefit post-retirement plans, which is measured as the difference between the fair value of the plan assets and the plan benefit obligations. We are also required to recognize changes in the funded status within accumulated other comprehensive income, net of tax, to the extent such changes are not recognized in earnings as components of periodic net benefit cost. The fair value of the plan assets was $133 million and $147 million as of December 31, 2018 and 2017, respectively. The total plan benefit obligations were $144 million and $165 million as of December 31, 2018 and 2017, respectively. Therefore, the net unfunded status was $11 million and $18 million as of December 31, 2018 and 2017, respectively.

Employee Benefits

Defined Contribution Plans

Prior to the CenturyLink acquisition on November 1, 2017, we offered our qualified employees the opportunity to participate in a defined contribution retirement plan qualifying under the provisions of Section 401(k) of the Internal Revenue Code ("401(k) Plan"). Each employee was eligible to contribute, on a tax deferred basis, a portion of annual earnings generally not to exceed $18,500 in 2018, $18,000 in 2017 and $18,000 in 2016. We matched 100% of employee contributions up to 4% of eligible earnings or applicable regulatory limits.

Effective December 31, 2017, the Level 3 Communications, Inc. 401(k) Profit Sharing Plan and Trust assets merged with the CenturyLink, Inc. Dollars & Sense 401(k) Plan. Those employees eligible to contribute to the Level 3 Plan at December 31, 2017 were automatically enrolled in the CenturyLink Plan at January 1, 2018. Provisions regarding eligibility, participant and employer contributions, vesting, and benefit payments within the Level 3 Plan document did not materially change and protected provisions applicable to Level 3 and its predecessor Plans remained grandfathered as required by law.

Prior to the CenturyLink acquisition on November 1, 2017, our matching contributions were made with Level 3 common stock based on the closing stock price on each pay date. After our acquisition, matching contributions were made in cash. We made 401(k) Plan matching contributions of $7 million for the successor period ended December 31, 2017, and $30 million and $37 million for the predecessor period ended October 31, 2017 and for the predecessor year ended December 31, 2016, respectively. Our matching contributions are recorded as compensation and included in cost of services of $1 million for the successor period ended December 31, 2017, and $4 million and $5 million for the predecessor period ended October 31, 2017 and for the predecessor year ended December 31, 2016, respectively. Our matching contributions included in selling, general and administrative expenses totaled $5 million for the successor period ended December 31, 2017, and $26 million and $32 million for the predecessor period ended October 31, 2017 and for the predecessor year ended December 31, 2016, respectively.

Other defined contribution plans we sponsored are individually not significant. On an aggregate basis, the expense we recorded relating to these plans was approximately $5 million and $1 million for the successor year ended December 31, 2018 and period ended December 31, 2017, and $5 million and $6 million for the predecessor period ended October 31, 2017 and for the predecessor year ended December 31, 2016, respectively.

Defined Benefit Plans

We have certain contributory and non-contributory employee pension plans, which are not significant to our financial position or operating results. We recognize in our balance sheet the funded status of our defined benefit post-retirement plans, which is measured as the difference between the fair value of the plan assets and the plan benefit obligations. We are also required to recognize changes in the funded status within accumulated other comprehensive income, net of tax, to the extent such changes are not recognized in earnings as components of periodic net benefit cost. The fair value of the plan assets was $133 million and $147 million as of December 31, 2018 and 2017, respectively. The total plan benefit obligations were $144 million and $165 million as of December 31, 2018 and 2017, respectively. Therefore, the net unfunded status was $11 million and $18 million as of December 31, 2018 and 2017, respectively.