Unaudited Quarterly Financial Data (Details) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015 USD ($) $ / shares	Sep. 30, 2015 USD ($) $ / shares	Jun. 30, 2015 USD ($) $ / shares	Mar. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($) $ / shares	Sep. 30, 2014 USD ($) $ / shares	Jun. 30, 2014 USD ($) $ / shares	Mar. 31, 2014 USD ($) $ / shares	Dec. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($) $ / shares	Dec. 31, 2013 USD ($) $ / shares	Nov. 13, 2015 USD ($)	Oct. 31, 2014 USD ($)	Aug. 12, 2014 USD ($)	Jul. 31, 2012 USD ($)	Jan. 13, 2012 USD ($)	Dec. 31, 2011	Jun. 09, 2011 USD ($)	Mar. 04, 2011 USD ($)
Selected Quarterly Financial Information [Abstract]
Revenue	$ 2,053	$ 2,062	$ 2,061	$ 2,053	$ 1,914	$ 1,629	$ 1,625	$ 1,609	$ 8,229	$ 6,777	$ 6,313
Network Access Costs	708	706	696	723	695	607	613	614	2,833	2,529	2,471
Network Related Expenses	344	369	363	356	345	307	302	292	1,432	1,246	1,214
Operating Income (Loss)	338	327	350	316	231	262	256	264	1,331	1,013	666
Interest Income	0	0	0	1	0	1	0	0	1	1	0
Interest Expense	(152)	(145)	(165)	(180)	(195)	(159)	(149)	(151)	(642)	(654)	(649)
Net Income (Loss)	$ 3,323	$ 1	$ (13)	$ 122	$ 66	$ 85	$ 51	$ 112	$ 3,433	$ 314	$ (109)
Net Income (Loss) Per Share -Basic | $ / shares	$ 9.33	$ 0	$ (0.04)	$ 0.35	$ 0.22	$ 0.36	$ 0.21	$ 0.48	$ 9.71	$ 1.23	$ (0.49)
Net Income (Loss) Per Share - Diluted | $ / shares	$ 9.24	$ 0	$ (0.04)	$ 0.35	$ 0.21	$ 0.35	$ 0.21	$ 0.47	$ 9.58	$ 1.21	$ (0.49)
Selling, General and Administrative Expenses	$ 369	$ 364	$ 364	$ 370	$ 393	$ 266	$ 267	$ 255	$ 1,467	$ 1,181	$ 1,162
Total Costs and Expenses	1,715	1,735	1,711	1,737	1,683	1,367	1,369	1,345	6,898	5,764	5,647
Depreciation expense									939	713	727
Depreciation and Amortization	294	296	288	288	250	187	187	184	1,166	808	800
Impairment of Intangible Assets (Excluding Goodwill)									17
Loss on modification and extinguishment of debt	(55)	0	(163)	0	(53)	0	0	0	(218)	(53)	(84)
Venezuela deconsolidation charge	0	(171)	0	0	0	0	0	0	(171)	0	0
Business Combination, Integration Related Costs					70				113
Other, net	3	6	(17)	(10)	(20)	(11)	(44)	6	(18)	(69)	(4)
Total Other Expense	(204)	(310)	(345)	(189)	(268)	(169)	(193)	(145)	(1,048)	(775)	(737)
Income (Loss) Before Income Taxes	134	17	5	127	(37)	93	63	119	283	238	(71)
Income Tax Expense (Benefit)	(3,189)	$ 16	18	$ 5	(103)	$ 8	12	$ 7	(3,150)	(76)	38
Recognized Income Tax Benefit	3,300				100
Foreign Currency Transaction Gain (Loss), before Tax							$ 34
Foreign Currency Exchange Rate, Translation		13.5					6.3
Foreign Currency Exchange Rate, Remeasurement							10.6
Property, Plant and Equipment, Gross	20,243				19,489				20,243	19,489
Long-term Debt, Gross	11,025				11,366				11,025	11,366
Asset Retirement Obligation, Revision of Estimate									$ 5	7
Senior Notes 5point 375Percent Due 2024 [Member]
Selected Quarterly Financial Information [Abstract]
Loss on modification and extinguishment of debt	$ (55)
Senior Notes 8 Point 625 Percent Due 2020 [Member]
Selected Quarterly Financial Information [Abstract]
Debt instrument, stated interest rate (as a percent)	8.625%								8.625%
Long-term Debt, Gross	$ 0				900				$ 0	900
Senior Notes due 2019 (9.375%)
Selected Quarterly Financial Information [Abstract]
Loss on modification and extinguishment of debt			(36)						$ (36)
Debt instrument, stated interest rate (as a percent)	9.375%								9.375%
Long-term Debt, Gross	$ 0				500				$ 0	500
Senior Notes due 2019 (8.125%)
Selected Quarterly Financial Information [Abstract]
Loss on modification and extinguishment of debt			(82)
Debt instrument, stated interest rate (as a percent)	8.125%								8.125%
Long-term Debt, Gross	$ 0				1,200				$ 0	1,200
Senior Notes due 2019 (8.875%)
Selected Quarterly Financial Information [Abstract]
Loss on modification and extinguishment of debt			(18)
Debt instrument, stated interest rate (as a percent)	8.875%								8.875%
Long-term Debt, Gross	$ 0				$ 300				$ 0	$ 300
Tranche B 2022 Term Loans [Member]
Selected Quarterly Financial Information [Abstract]
Loss on modification and extinguishment of debt			$ 27
Debt instrument, stated interest rate (as a percent)					4.50%					4.50%
Long-term Debt, Gross	$ 0				$ 2,000				$ 0	$ 2,000
Tranche B-II Term Loans and Senior Notes [Member]
Selected Quarterly Financial Information [Abstract]
Loss on modification and extinguishment of debt					53
Senior Notes 11 Point 875 Percent Due 2019 [Member]
Selected Quarterly Financial Information [Abstract]
Debt instrument, stated interest rate (as a percent)	11.875%								11.875%
TrancheB2022TermLoanTotal [Member]
Selected Quarterly Financial Information [Abstract]
Long-term Debt, Gross	$ 2,000								$ 2,000
Senior Notes 5.375percent Due 2022 [Member]
Selected Quarterly Financial Information [Abstract]
Debt Instrument, Face Amount	$ 1,000								$ 1,000					$ 1,000
Debt instrument, stated interest rate (as a percent)	5.375%								5.375%
Floating Rate Senior Notes due 2015 [Member]
Selected Quarterly Financial Information [Abstract]
Debt instrument, stated interest rate (as a percent)	3.846%								3.846%								3.826%
Level 3 Financing [Member] | Senior Notes 5point 375Percent Due 2024 [Member]
Selected Quarterly Financial Information [Abstract]
Loss on modification and extinguishment of debt									$ (55)
Debt Instrument, Face Amount												$ 900
Debt instrument, stated interest rate (as a percent)	5.375%								5.375%
Level 3 Financing [Member] | Senior Notes 8 Point 625 Percent Due 2020 [Member]
Selected Quarterly Financial Information [Abstract]
Debt Instrument, Face Amount																$ 900
Debt instrument, stated interest rate (as a percent)	8.625%								8.625%
Level 3 Financing [Member] | Senior Notes due 2019 (9.375%)
Selected Quarterly Financial Information [Abstract]
Debt Instrument, Face Amount																			$ 500
Debt instrument, stated interest rate (as a percent)	9.375%								9.375%
Level 3 Financing [Member] | Senior Notes due 2019 (8.125%)
Selected Quarterly Financial Information [Abstract]
Loss on modification and extinguishment of debt									$ (82)
Debt Instrument, Face Amount																		$ 1,200
Debt instrument, stated interest rate (as a percent)	8.125%								8.125%
Level 3 Financing [Member] | Senior Notes due 2019 (8.875%)
Selected Quarterly Financial Information [Abstract]
Loss on modification and extinguishment of debt									$ (18)
Debt Instrument, Face Amount															$ 300
Level 3 Financing [Member] | Tranche B 2022 Term Loans [Member]
Selected Quarterly Financial Information [Abstract]
Loss on modification and extinguishment of debt									$ 27
Debt Instrument, Face Amount													$ 2,000
Level 3 Financing [Member] | Senior Notes 5.375percent Due 2022 [Member]
Selected Quarterly Financial Information [Abstract]
Debt instrument, stated interest rate (as a percent)	5.375%								5.375%
Level 3 Escrow II, Inc. [Member] | Senior Notes 5.375percent Due 2022 [Member]
Selected Quarterly Financial Information [Abstract]
Debt Instrument, Face Amount														$ 1,000
Guarantor Subsidiaries [Member]
Selected Quarterly Financial Information [Abstract]
Revenue									$ 0	0	0
Network Access Costs									0	0	0
Network Related Expenses									0	0	0
Operating Income (Loss)									0	(2)	(1)
Interest Income									0	0	0
Interest Expense									(574)	(492)	(497)
Net Income (Loss)									2,162	(710)
Selling, General and Administrative Expenses									0	2	1
Total Costs and Expenses									0	2	1
Depreciation and Amortization									0	0	0
Total Other Expense									(483)	(712)	(1,040)
Income (Loss) Before Income Taxes									(483)	(714)	(1,041)
Income Tax Expense (Benefit)									(2,645)	(4)	(2)
Guarantor Subsidiaries [Member] | TrancheB2022TermLoanTotal [Member]
Selected Quarterly Financial Information [Abstract]
Long-term Debt, Gross	$ 2,000								2,000
Level 3 Communications, Inc.
Selected Quarterly Financial Information [Abstract]
Revenue									0	0	0
Network Access Costs									0	0	0
Network Related Expenses									0	0	0
Operating Income (Loss)									(4)	(21)	(3)
Interest Income									0	0	0
Interest Expense									(51)	(143)	(151)
Net Income (Loss)									3,433	314
Selling, General and Administrative Expenses									4	21	3
Total Costs and Expenses									4	21	3
Depreciation and Amortization									0	0	0
Total Other Expense									3,403	321	(99)
Income (Loss) Before Income Taxes									3,399	300	(102)
Income Tax Expense (Benefit)									$ (34)	$ (14)	$ 7
Level 3 Communications, Inc. | Senior Notes due 2019 (8.875%)
Selected Quarterly Financial Information [Abstract]
Debt instrument, stated interest rate (as a percent)	8.875%								8.875%
Level 3 Communications, Inc. | Senior Notes 11 Point 875 Percent Due 2019 [Member]
Selected Quarterly Financial Information [Abstract]
Loss on modification and extinguishment of debt					$ (53)
Debt instrument, stated interest rate (as a percent)	11.875%								11.875%