Condensed Consolidating Financial Information - Statements of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Condensed Consolidating Financial Information
Net Cash Provided by (Used in) Operating Activities			$ 1,786	$ 1,299
Cash Flows from Investing Activities:
Capital expenditures	$ (364)	$ (328)	(1,028)	(899)
Cash related to deconsolidated Venezuela operations			0	(83)
(Increase) decrease in restricted cash and securities, net			11	(24)
Proceeds from sale of property, plant, and equipment and other assets			1	3
Other			0	(14)
Net Cash Used in Investing Activities			(1,016)	(1,017)
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs			764	3,947
Payments on and repurchases of long-term debt and capital leases			(818)	(4,102)
Increase (decrease) due from-to affiliates, net			0	0
Net Cash Provided by (Used in) Financing Activities			(54)	(155)
Effect of Exchange Rates on Cash and Cash Equivalents			(1)	(16)
Net Change in Cash and Cash Equivalents			715	111
Cash and Cash Equivalents at Beginning of Period			854	580
Cash and Cash Equivalents at End of Period	1,569	691	1,569	691
Level 3 Communications, Inc.
Condensed Consolidating Financial Information
Net Cash Provided by (Used in) Operating Activities			(35)	(39)
Cash Flows from Investing Activities:
Capital expenditures			0	0
Cash related to deconsolidated Venezuela operations				0
(Increase) decrease in restricted cash and securities, net			5	(25)
Proceeds from sale of property, plant, and equipment and other assets			0	0
Other				0
Net Cash Used in Investing Activities			5	(25)
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs			0	0
Payments on and repurchases of long-term debt and capital leases			0	(313)
Increase (decrease) due from-to affiliates, net			34	383
Net Cash Provided by (Used in) Financing Activities			34	70
Effect of Exchange Rates on Cash and Cash Equivalents			0	0
Net Change in Cash and Cash Equivalents			4	6
Cash and Cash Equivalents at Beginning of Period			12	7
Cash and Cash Equivalents at End of Period	16	13	16	13
Level 3 Financing, Inc.
Condensed Consolidating Financial Information
Net Cash Provided by (Used in) Operating Activities			(332)	(447)
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
Net Cash Used in Investing Activities			0	0
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs			764	3,947
Payments on and repurchases of long-term debt and capital leases			(806)	(3,780)
Increase (decrease) due from-to affiliates, net			368	281
Net Cash Provided by (Used in) Financing Activities			326	448
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			6	5
Cash and Cash Equivalents at End of Period	0	6	0	6
Level 3 Communications, LLC
Condensed Consolidating Financial Information
Net Cash Provided by (Used in) Operating Activities			489	57
Cash Flows from Investing Activities:
Capital expenditures			(537)	(307)
Cash related to deconsolidated Venezuela operations				0
(Increase) decrease in restricted cash and securities, net			6	1
Proceeds from sale of property, plant, and equipment and other assets			0	0
Other				(14)
Net Cash Used in Investing Activities			(531)	(320)
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs			0	0
Payments on and repurchases of long-term debt and capital leases			(1)	(1)
Increase (decrease) due from-to affiliates, net			798	516
Net Cash Provided by (Used in) Financing Activities			797	515
Effect of Exchange Rates on Cash and Cash Equivalents			0	0
Net Change in Cash and Cash Equivalents			755	252
Cash and Cash Equivalents at Beginning of Period			727	307
Cash and Cash Equivalents at End of Period	1,482	559	1,482	559
Other Non-Guarantor Subsidiaries
Condensed Consolidating Financial Information
Net Cash Provided by (Used in) Operating Activities			1,664	1,728
Cash Flows from Investing Activities:
Capital expenditures			(491)	(592)
Cash related to deconsolidated Venezuela operations				(83)
(Increase) decrease in restricted cash and securities, net			0	0
Proceeds from sale of property, plant, and equipment and other assets			1	3
Other				0
Net Cash Used in Investing Activities			(490)	(672)
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs			0	0
Payments on and repurchases of long-term debt and capital leases			(11)	(8)
Increase (decrease) due from-to affiliates, net			(1,200)	(1,180)
Net Cash Provided by (Used in) Financing Activities			(1,211)	(1,188)
Effect of Exchange Rates on Cash and Cash Equivalents			(1)	(16)
Net Change in Cash and Cash Equivalents			(38)	(148)
Cash and Cash Equivalents at Beginning of Period			109	261
Cash and Cash Equivalents at End of Period	71	113	71	113
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
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 and capital leases			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