Condensed Consolidating Financial Information - Statements of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Condensed Consolidating Financial Information
Net Cash Provided by (Used in) Operating Activities			$ 724	$ 444
Cash Flows from Investing Activities:
Capital expenditures	$ (317)	$ (241)	(571)	(404)
(Increase) decrease in restricted cash and securities, net			(24)	2
Proceeds from sale of property, plant, and equipment and other assets			2
Net Cash Provided by (Used in) Investing Activities			(593)	(402)
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs			3,948
Payments on and repurchases of long-term debt, including current portions and refinancing costs			(4,098)	(6)
Increase (decrease) due from-to affiliates, net			0	0
Net Cash Provided by (Used in) Financing Activities			(150)	(6)
Effect of Exchange Rates on Cash and Cash Equivalents			(12)	(30)
Net Change in Cash and Cash Equivalents			(31)	6
Cash and Cash Equivalents at Beginning of Period			580	631
Cash and Cash Equivalents at End of Period	549	637	549	637
Level 3 Communications, Inc.
Condensed Consolidating Financial Information
Net Cash Provided by (Used in) Operating Activities			(21)	(66)
Cash Flows from Investing Activities:
Capital expenditures			0	0
(Increase) decrease in restricted cash and securities, net			(25)	0
Proceeds from sale of property, plant, and equipment and other assets			0
Net Cash Provided by (Used in) Investing Activities			(25)	0
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs			0
Payments on and repurchases of long-term debt, including current portions and refinancing costs			(313)	0
Increase (decrease) due from-to affiliates, net			365	66
Net Cash Provided by (Used in) Financing Activities			52	66
Effect of Exchange Rates on Cash and Cash Equivalents			0	0
Net Change in Cash and Cash Equivalents			6	0
Cash and Cash Equivalents at Beginning of Period			7	8
Cash and Cash Equivalents at End of Period	13	8	13	8
Level 3 Financing, Inc.
Condensed Consolidating Financial Information
Net Cash Provided by (Used in) Operating Activities			(339)	(222)
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
Net Cash Provided by (Used in) Investing Activities			0	0
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs			3,948
Payments on and repurchases of long-term debt, including current portions and refinancing costs			(3,780)	0
Increase (decrease) due from-to affiliates, net			171	222
Net Cash Provided by (Used in) Financing Activities			339	222
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			5	6
Cash and Cash Equivalents at End of Period	5	6	5	6
Level 3 Communications, LLC
Condensed Consolidating Financial Information
Net Cash Provided by (Used in) Operating Activities			(22)	370
Cash Flows from Investing Activities:
Capital expenditures			(188)	(192)
(Increase) decrease in restricted cash and securities, net			1	0
Proceeds from sale of property, plant, and equipment and other assets			0
Net Cash Provided by (Used in) Investing Activities			(187)	(192)
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs			0
Payments on and repurchases of long-term debt, including current portions and refinancing costs			0	0
Increase (decrease) due from-to affiliates, net			191	(111)
Net Cash Provided by (Used in) Financing Activities			191	(111)
Effect of Exchange Rates on Cash and Cash Equivalents			0	0
Net Change in Cash and Cash Equivalents			(18)	67
Cash and Cash Equivalents at Beginning of Period			307	347
Cash and Cash Equivalents at End of Period	289	414	289	414
Other Non-Guarantor Subsidiaries
Condensed Consolidating Financial Information
Net Cash Provided by (Used in) Operating Activities			1,106	362
Cash Flows from Investing Activities:
Capital expenditures			(383)	(212)
(Increase) decrease in restricted cash and securities, net			0	2
Proceeds from sale of property, plant, and equipment and other assets			2
Net Cash Provided by (Used in) Investing Activities			(381)	(210)
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs			0
Payments on and repurchases of long-term debt, including current portions and refinancing costs			(5)	(6)
Increase (decrease) due from-to affiliates, net			(727)	(177)
Net Cash Provided by (Used in) Financing Activities			(732)	(183)
Effect of Exchange Rates on Cash and Cash Equivalents			(12)	(30)
Net Change in Cash and Cash Equivalents			(19)	(61)
Cash and Cash Equivalents at Beginning of Period			261	270
Cash and Cash Equivalents at End of Period	242	209	242	209
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
Net Cash Provided by (Used in) Investing Activities			0	0
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs			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