Condensed Consolidating Financial Information - Statements of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Condensed Consolidating Financial Information
Net Cash Provided by Operating Activities	$ 2,343	$ 1,855	$ 1,161
Cash Flows from Investing Activities:
Capital expenditures	(1,334)	(1,229)	(910)
Cash related to deconsolidated Venezuela operations	0	(83)	0
Increase (Decrease) in Restricted Cash and Investments	12	(22)	(10)
Proceeds from sale of property, plant and equipment and other assets	3	4	3
Payments to Acquire Businesses, Net of Cash Acquired	0	0	(167)
Other	0	(14)	(2)
Net Cash Used in Investing Activities	(1,319)	(1,344)	(1,086)
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs	764	4,832	589
Payments on and repurchases of long-term debt, including current portions and refinancing costs	(820)	(5,051)	(671)
Increase (decrease) due from affiliates, net	0	0	0
Net Cash Used in Financing Activities	(56)	(219)	(82)
Effect of Exchange Rates on Cash and Cash Equivalents	(3)	(18)	(44)
Net Change in Cash and Cash Equivalents	965	274	(51)
Cash and Cash Equivalents at Beginning of Year	854	580	631
Cash and Cash Equivalents at End of Year	1,819	854	580
Level 3 Communications, Inc.
Condensed Consolidating Financial Information
Net Cash Provided by Operating Activities	(49)	(40)	(178)
Cash Flows from Investing Activities:
Capital expenditures	0	0	0
Cash related to deconsolidated Venezuela operations		0
Increase (Decrease) in Restricted Cash and Investments	5	(25)	0
Proceeds from sale of property, plant and equipment and other assets	0	0	0
Payments to Acquire Businesses, Net of Cash Acquired			(474)
Other		0	0
Net Cash Used in Investing Activities	5	(25)	(474)
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs	0	0	590
Payments on and repurchases of long-term debt, including current portions and refinancing costs	0	(313)	(647)
Increase (decrease) due from affiliates, net	47	383	708
Net Cash Used in Financing Activities	47	70	651
Effect of Exchange Rates on Cash and Cash Equivalents	0	0	0
Net Change in Cash and Cash Equivalents	3	5	(1)
Cash and Cash Equivalents at Beginning of Year	12	7	8
Cash and Cash Equivalents at End of Year	15	12	7
Level 3 Financing, Inc.
Condensed Consolidating Financial Information
Net Cash Provided by Operating Activities	(468)	(617)	(458)
Cash Flows from Investing Activities:
Capital expenditures	0	0	0
Cash related to deconsolidated Venezuela operations		0
Increase (Decrease) in Restricted Cash and Investments	0	0	0
Proceeds from sale of property, plant and equipment and other assets	0	0	0
Payments to Acquire Businesses, Net of Cash Acquired			0
Other		0	0
Net Cash Used in Investing Activities	0	0	0
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs	764	4,832	0
Payments on and repurchases of long-term debt, including current portions and refinancing costs	(806)	(4,725)	0
Increase (decrease) due from affiliates, net	504	511	457
Net Cash Used in Financing Activities	462	618	457
Effect of Exchange Rates on Cash and Cash Equivalents	0	0	0
Net Change in Cash and Cash Equivalents	(6)	1	(1)
Cash and Cash Equivalents at Beginning of Year	6	5	6
Cash and Cash Equivalents at End of Year	0	6	5
Level 3 Communications, LLC
Condensed Consolidating Financial Information
Net Cash Provided by Operating Activities	564	193	625
Cash Flows from Investing Activities:
Capital expenditures	(704)	(453)	(362)
Cash related to deconsolidated Venezuela operations		0
Increase (Decrease) in Restricted Cash and Investments	6	3	2
Proceeds from sale of property, plant and equipment and other assets	(1)	0	0
Payments to Acquire Businesses, Net of Cash Acquired			0
Other		(14)	0
Net Cash Used in Investing Activities	(697)	(464)	(360)
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs	0	0	0
Payments on and repurchases of long-term debt, including current portions and refinancing costs	(1)	(2)	0
Increase (decrease) due from affiliates, net	1,107	693	(305)
Net Cash Used in Financing Activities	1,106	691	(305)
Effect of Exchange Rates on Cash and Cash Equivalents	0	0	0
Net Change in Cash and Cash Equivalents	973	420	(40)
Cash and Cash Equivalents at Beginning of Year	727	307	347
Cash and Cash Equivalents at End of Year	1,700	727	307
Other Non-Guarantor Subsidiaries
Condensed Consolidating Financial Information
Net Cash Provided by Operating Activities	2,296	2,319	1,172
Cash Flows from Investing Activities:
Capital expenditures	(630)	(776)	(548)
Cash related to deconsolidated Venezuela operations		(83)
Increase (Decrease) in Restricted Cash and Investments	1	0	(12)
Proceeds from sale of property, plant and equipment and other assets	2	4	3
Payments to Acquire Businesses, Net of Cash Acquired			307
Other		0	(2)
Net Cash Used in Investing Activities	(627)	(855)	(252)
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs	0	0	(1)
Payments on and repurchases of long-term debt, including current portions and refinancing costs	(13)	(11)	(24)
Increase (decrease) due from affiliates, net	(1,658)	(1,587)	(860)
Net Cash Used in Financing Activities	(1,671)	(1,598)	(885)
Effect of Exchange Rates on Cash and Cash Equivalents	(3)	(18)	(44)
Net Change in Cash and Cash Equivalents	(5)	(152)	(9)
Cash and Cash Equivalents at Beginning of Year	109	261	270
Cash and Cash Equivalents at End of Year	104	109	261
Eliminations
Condensed Consolidating Financial Information
Net Cash Provided by Operating Activities	0	0	0
Cash Flows from Investing Activities:
Capital expenditures	0	0	0
Cash related to deconsolidated Venezuela operations		0
Increase (Decrease) in Restricted Cash and Investments	0	0	0
Proceeds from sale of property, plant and equipment and other assets	0	0	0
Payments to Acquire Businesses, Net of Cash Acquired			0
Other		0	0
Net Cash Used in Investing Activities	0	0	0
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs	0	0	0
Payments on and repurchases of long-term debt, including current portions and refinancing costs	0	0	0
Increase (decrease) due from affiliates, net	0	0	0
Net Cash Used in Financing Activities	0	0	0
Effect of Exchange Rates on Cash and Cash Equivalents	0	0	0
Net Change in Cash and Cash Equivalents	0	0	0
Cash and Cash Equivalents at Beginning of Year	0	0	0
Cash and Cash Equivalents at End of Year	$ 0	$ 0	$ 0

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