Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Description of the interest rate as being fixed or variable, and, if variable, identification of the index or rate on which the interest rate is based and the number of points or percentage added to that index or rate to set the rate, and other pertinent information, such as frequency of rate resets.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount, after accumulated amortization, of debt discount (premium).

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Amount of long-term debt and capital lease obligation due after one year or beyond the normal operating cycle, if longer.

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Amount of long-term debt and capital leases due within one year or the normal operating cycle, if longer.

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The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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Long-Term Debt - Schedule of Long Term Debt (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Feb. 22, 2017	Dec. 31, 2016	Sep. 30, 2016	Apr. 21, 2016	Mar. 22, 2016
Long-term debt
Total Debt Obligations	$ 10,705		$ 11,009
Total Unamortized Discount	0		13
Unamortized Debt Issuance Expense	(112)		(112)
Current portion of long-term debt	(7)		(7)
Long-Term Debt, less current portion	10,586		10,877
Tranche B-III 2019 Term Loan
Long-term debt
Total Debt Obligations	0		815
TrancheB2020TermLoanTotal [Member]
Long-term debt
Total Debt Obligations	$ 0		1,796
Floating Rate Senior Notes due 2018
Long-term debt
Debt Instrument, Interest Rate Terms	6-Month LIBOR +3.50%
Total Debt Obligations	$ 0		$ 300
2.0 Billion Tranche B-II 2022 Term Loan [Member]
Long-term debt
Debt Instrument, Interest Rate Terms	LIBOR +2.75%
Stated interest rate (as a percent)			3.50%
Total Debt Obligations	$ 0		$ 2,000
Tranche B Two Thousand Twenty Four Term Loan [Member]
Long-term debt
Debt Instrument, Interest Rate Terms	LIBOR +2.25%
Stated interest rate (as a percent)	3.486%
Total Debt Obligations	$ 4,611	$ 4,611
SeniorNotes6Point125PercentDue2021 [Member]
Long-term debt
Total Debt Obligations	640		640
5point375SeniorNotesdue2022 [Member]
Long-term debt
Total Debt Obligations	1,000		1,000
Senior Notes 5point75Percent Due 2022 [Member]
Long-term debt
Total Debt Obligations	600		600
Senior Notes 5point 625Percent Due 2023 [Member]
Long-term debt
Total Debt Obligations	500		500
Senior Notes 5.375 Percent Due 2024 [Member]
Long-term debt
Total Debt Obligations	900		900
Senior Notes 5point 125Percent Due 2023 [Member]
Long-term debt
Total Debt Obligations	700		700
Senior Notes 5point 375Percent Due 2025 [Member]
Long-term debt
Total Debt Obligations	800		800
Capital Leases
Long-term debt
Total Debt Obligations	179		183
Level 3 Communications, LLC
Long-term debt
Current portion of long-term debt	(2)		(2)
Long-Term Debt, less current portion	$ 13		$ 13
Level 3 Communications, LLC \| Tranche B-III 2019 Term Loan
Long-term debt
Debt Instrument, Interest Rate Terms	LIBOR +3.00%
Level 3 Communications, LLC \| TrancheB2020TermLoanTotal [Member]
Long-term debt
Debt Instrument, Interest Rate Terms	LIBOR +3.00%
Level 3 Financing [Member] \| Floating Rate Senior Notes due 2018
Long-term debt
Stated interest rate (as a percent)			4.762%
Level 3 Financing [Member] \| 7.0% Senior Notes due 2020
Long-term debt
Stated interest rate (as a percent)	7.00%				7.00%
Level 3 Financing [Member] \| SeniorNotes6Point125PercentDue2021 [Member]
Long-term debt
Stated interest rate (as a percent)	6.125%
Level 3 Financing [Member] \| 5.37percent Senior Notes Due 2022 [Member]
Long-term debt
Stated interest rate (as a percent)	5.375%
Level 3 Financing [Member] \| Senior Notes 5point 625Percent Due 2023 [Member]
Long-term debt
Stated interest rate (as a percent)	5.625%
Level 3 Financing [Member] \| Senior Notes 5point 125Percent Due 2023 [Member]
Long-term debt
Stated interest rate (as a percent)	5.125%
Level 3 Financing [Member] \| Senior Notes 5point 375Percent Due 2024 [Member]
Long-term debt
Stated interest rate (as a percent)	5.375%
Level 3 Financing [Member] \| Senior Notes 5point 375Percent Due 2025 [Member]
Long-term debt
Stated interest rate (as a percent)	5.375%
Level 3 Financing [Member] \| Senior Notes 5point 250Percent Due 2026 [Member]
Long-term debt
Stated interest rate (as a percent)	5.25%			5.25%	5.25%
Total Debt Obligations	$ 775		$ 775			$ 775
Parent Company [Member]
Long-term debt
Current portion of long-term debt	0		0
Long-Term Debt, less current portion	$ 593		$ 592
Parent Company [Member] \| Senior Notes 5point75Percent Due 2022 [Member]
Long-term debt
Stated interest rate (as a percent)	5.75%