Condensed Consolidating Financial Information - Statements of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Condensed Consolidating Financial Information
Net Cash Provided by (Used in) Operating Activities			$ 1,299	$ 765
Cash Flows from Investing Activities:
Capital expenditures	$ (328)	$ (204)	(899)	(608)
Cash related to deconsolidated Venezuela operations	(83)		(83)	0
(Increase) decrease in restricted cash and securities, net			(24)	(10)
Proceeds from sale of property, plant, and equipment and other assets			3	3
Other			14	2
Net Cash Used in Investing Activities			(1,017)	(617)
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs			3,947	(1)
Payments on and repurchases of long-term debt, including current portions and refinancing costs			(4,102)	(8)
Increase (decrease) due from-to affiliates, net			0	0
Net Cash Provided by (Used in) Financing Activities			(155)	(9)
Effect of Exchange Rates on Cash and Cash Equivalents			(16)	(41)
Net Change in Cash and Cash Equivalents			111	98
Cash and Cash Equivalents at Beginning of Period			580	631
Cash and Cash Equivalents at End of Period	691	729	691	729
Level 3 Communications, Inc.
Condensed Consolidating Financial Information
Net Cash Provided by (Used in) Operating Activities			(39)	(91)
Cash Flows from Investing Activities:
Capital expenditures			0	0
Cash related to deconsolidated Venezuela operations			0
(Increase) decrease in restricted cash and securities, net			(25)	0
Proceeds from sale of property, plant, and equipment and other assets			0	0
Other			0	0
Net Cash Used in Investing Activities			(25)	0
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs			0	0
Payments on and repurchases of long-term debt, including current portions and refinancing costs			(313)	0
Increase (decrease) due from-to affiliates, net			383	90
Net Cash Provided by (Used in) Financing Activities			70	90
Effect of Exchange Rates on Cash and Cash Equivalents			0	0
Net Change in Cash and Cash Equivalents			6	(1)
Cash and Cash Equivalents at Beginning of Period			7	8
Cash and Cash Equivalents at End of Period	13	7	13	7
Level 3 Financing, Inc.
Condensed Consolidating Financial Information
Net Cash Provided by (Used in) Operating Activities			(447)	(336)
Cash Flows from Investing Activities:
Capital expenditures			0	0
Cash related to deconsolidated Venezuela operations			0
(Increase) decrease in restricted cash and securities, net			0	0
Proceeds from sale of property, plant, and equipment and other assets			0	0
Other			0	0
Net Cash Used in Investing Activities			0	0
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs			3,947	0
Payments on and repurchases of long-term debt, including current portions and refinancing costs			(3,780)	0
Increase (decrease) due from-to affiliates, net			281	335
Net Cash Provided by (Used in) Financing Activities			448	335
Effect of Exchange Rates on Cash and Cash Equivalents			0	0
Net Change in Cash and Cash Equivalents			1	(1)
Cash and Cash Equivalents at Beginning of Period			5	6
Cash and Cash Equivalents at End of Period	6	5	6	5
Level 3 Communications, LLC
Condensed Consolidating Financial Information
Net Cash Provided by (Used in) Operating Activities			57	443
Cash Flows from Investing Activities:
Capital expenditures			(307)	(261)
Cash related to deconsolidated Venezuela operations			0
(Increase) decrease in restricted cash and securities, net			1	1
Proceeds from sale of property, plant, and equipment and other assets			0	0
Other			14	0
Net Cash Used in Investing Activities			(320)	(260)
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs			0	0
Payments on and repurchases of long-term debt, including current portions and refinancing costs			(1)	0
Increase (decrease) due from-to affiliates, net			516	(6)
Net Cash Provided by (Used in) Financing Activities			515	(6)
Effect of Exchange Rates on Cash and Cash Equivalents			0	0
Net Change in Cash and Cash Equivalents			252	177
Cash and Cash Equivalents at Beginning of Period			307	347
Cash and Cash Equivalents at End of Period	559	524	559	524
Other Non-Guarantor Subsidiaries
Condensed Consolidating Financial Information
Net Cash Provided by (Used in) Operating Activities			1,728	749
Cash Flows from Investing Activities:
Capital expenditures			(592)	(347)
Cash related to deconsolidated Venezuela operations			(83)
(Increase) decrease in restricted cash and securities, net			0	(11)
Proceeds from sale of property, plant, and equipment and other assets			3	3
Other			0	2
Net Cash Used in Investing Activities			(672)	(357)
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs			0	(1)
Payments on and repurchases of long-term debt, including current portions and refinancing costs			(8)	(8)
Increase (decrease) due from-to affiliates, net			(1,180)	(419)
Net Cash Provided by (Used in) Financing Activities			(1,188)	(428)
Effect of Exchange Rates on Cash and Cash Equivalents			(16)	(41)
Net Change in Cash and Cash Equivalents			(148)	(77)
Cash and Cash Equivalents at Beginning of Period			261	270
Cash and Cash Equivalents at End of Period	113	193	113	193
Eliminations
Condensed Consolidating Financial Information
Net Cash Provided by (Used in) Operating Activities			0	0
Cash Flows from Investing Activities:
Capital expenditures			0	0
(Increase) decrease in restricted cash and securities, net			0	0
Proceeds from sale of property, plant, and equipment and other assets			0	0
Other			0	0
Net Cash Used in Investing Activities			0	0
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs			0	0
Payments on and repurchases of long-term debt, including current portions and refinancing costs			0	0
Increase (decrease) due from-to affiliates, net			0	0
Net Cash Provided by (Used in) Financing Activities			0	0
Effect of Exchange Rates on Cash and Cash Equivalents			0	0
Net Change in Cash and Cash Equivalents			0	0
Cash and Cash Equivalents at Beginning of Period			0	0
Cash and Cash Equivalents at End of Period	$ 0	$ 0	$ 0	$ 0