Condensed Consolidating Financial Information - Statements of Cash Flows (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Condensed Consolidating Financial Information
Net Cash Provided by (Used in) Operating Activities	$ 305	$ 141
Cash Flows from Investing Activities:
Capital expenditures	(254)	(163)
(Increase) decrease in restricted cash and securities, net	1	1
Proceeds from sale of property, plant, and equipment and other assets	1	1
Other	0	1
Net Cash Provided by (Used in) Investing Activities	(252)	(162)
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs	492	0
Payments on and repurchases of long-term debt, including current portions and refinancing costs	(2)	(3)
Increase (decrease) due from-to affiliates, net	0	0
Net Cash Provided by (Used in) Financing Activities	490	(3)
Effect of Exchange Rates on Cash and Cash Equivalents	(9)	0
Net Change in Cash and Cash Equivalents	534	(24)
Cash and Cash Equivalents at Beginning of Period	580	631
Cash and Cash Equivalents at End of Period	1,114	607
Level 3 Communications, Inc.
Condensed Consolidating Financial Information
Net Cash Provided by (Used in) Operating Activities	(7)	(16)
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 Provided by (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	14	16
Net Cash Provided by (Used in) Financing Activities	14	16
Effect of Exchange Rates on Cash and Cash Equivalents	0	0
Net Change in Cash and Cash Equivalents	7	0
Cash and Cash Equivalents at Beginning of Period	7	8
Cash and Cash Equivalents at End of Period	14	8
Level 3 Financing, Inc.
Condensed Consolidating Financial Information
Net Cash Provided by (Used in) Operating Activities	(137)	(125)
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 Provided by (Used in) Investing Activities	0	0
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs	492	0
Payments on and repurchases of long-term debt, including current portions and refinancing costs	0	0
Increase (decrease) due from-to affiliates, net	(355)	125
Net Cash Provided by (Used in) Financing Activities	137	125
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
Level 3 Communications, LLC
Condensed Consolidating Financial Information
Net Cash Provided by (Used in) Operating Activities	(82)	183
Cash Flows from Investing Activities:
Capital expenditures	(77)	(74)
(Increase) decrease in restricted cash and securities, net	1	0
Proceeds from sale of property, plant, and equipment and other assets	0	0
Other	0	0
Net Cash Provided by (Used in) Investing Activities	(76)	(74)
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	692	(100)
Net Cash Provided by (Used in) Financing Activities	692	(100)
Effect of Exchange Rates on Cash and Cash Equivalents	0	0
Net Change in Cash and Cash Equivalents	534	9
Cash and Cash Equivalents at Beginning of Period	307	347
Cash and Cash Equivalents at End of Period	841	356
Other Non-Guarantor Subsidiaries
Condensed Consolidating Financial Information
Net Cash Provided by (Used in) Operating Activities	531	99
Cash Flows from Investing Activities:
Capital expenditures	(177)	(89)
(Increase) decrease in restricted cash and securities, net	0	1
Proceeds from sale of property, plant, and equipment and other assets	1	1
Other	0	1
Net Cash Provided by (Used in) Investing Activities	(176)	(88)
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	(2)	(3)
Increase (decrease) due from-to affiliates, net	(351)	(41)
Net Cash Provided by (Used in) Financing Activities	(353)	(44)
Effect of Exchange Rates on Cash and Cash Equivalents	(9)	0
Net Change in Cash and Cash Equivalents	(7)	(33)
Cash and Cash Equivalents at Beginning of Period	261	270
Cash and Cash Equivalents at End of Period	254	237
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 Provided by (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