Condensed Consolidating Financial Information - Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2010
Current Assets:
Cash and cash equivalents	$ 854	$ 580	$ 631	$ 979	$ 979
Restricted cash and securities	8	7
Receivables, less allowances for doubtful accounts	757	737
Due from affiliates	0	0
Other	130	157
Total Current Assets	1,749	1,481
Property, Plant and Equipment, net	9,878	9,860
Restricted Cash and Securities	42	20
Goodwill and Other Intangibles Assets, net	8,876	9,103
Investment in Subsidiaries	0	0
Deferred Tax Assets	3,441	300
Other Assets, net	159	183
Total Assets	24,145	20,947
Liabilities:
Accounts payable	629	664
Current portion of long-term debt	15	349
Accrued payroll and employee benefits	218	273
Accrued interest	108	174
Current portion of deferred revenue	267	287
Due to affiliates	0	0
Other	179	159
Total Current Liabilities	1,416	1,906
Long-Term Debt, less current portion	10,994	10,984
Deferred Revenue, less current portion	977	921
Other Liabilities	632	773
Commitments and Contingencies	0	0
Stockholders' Equity (Deficit)	10,126	6,363	1,411	$ 1,171
Total Liabilities and Stockholders’ Equity	24,145	20,947
Level 3 Communications, Inc.
Current Assets:
Cash and cash equivalents	12	7	8		253
Restricted cash and securities	0	0
Receivables, less allowances for doubtful accounts	0	0
Due from affiliates	12,415	14,522
Other	1	2
Total Current Assets	12,428	14,531
Property, Plant and Equipment, net	0	0
Restricted Cash and Securities	27	3
Goodwill and Other Intangibles Assets, net	0	0
Investment in Subsidiaries	16,772	16,686
Deferred Tax Assets	38	0
Other Assets, net	8	28
Total Assets	29,273	31,248
Liabilities:
Accounts payable	0	0
Current portion of long-term debt	0	333
Accrued payroll and employee benefits	0	0
Accrued interest	11	12
Current portion of deferred revenue	0	0
Due to affiliates	0	0
Other	0	0
Total Current Liabilities	11	345
Long-Term Debt, less current portion	600	900
Deferred Revenue, less current portion	0	0
Other Liabilities	15	16
Stockholders' Equity (Deficit)	28,647	29,987
Total Liabilities and Stockholders’ Equity	29,273	31,248
Level 3 Financing, Inc.
Current Assets:
Cash and cash equivalents	6	5	6		5
Restricted cash and securities	0	0
Receivables, less allowances for doubtful accounts	0	0
Due from affiliates	22,759	21,270
Other	18	21
Total Current Assets	22,783	21,296
Property, Plant and Equipment, net	0	0
Restricted Cash and Securities	0	0
Goodwill and Other Intangibles Assets, net	0	0
Investment in Subsidiaries	17,714	14,777
Deferred Tax Assets	2,847	0
Other Assets, net	100	129
Total Assets	43,444	36,202
Liabilities:
Accounts payable	1	0
Current portion of long-term debt	0	0
Accrued payroll and employee benefits	0	0
Accrued interest	90	158
Current portion of deferred revenue	0	0
Due to affiliates	0	0
Other	0	2
Total Current Liabilities	91	160
Long-Term Debt, less current portion	10,210	9,893
Deferred Revenue, less current portion	0	0
Other Liabilities	0	24
Stockholders' Equity (Deficit)	33,143	26,125
Total Liabilities and Stockholders’ Equity	43,444	36,202
Level 3 Communications, LLC
Current Assets:
Cash and cash equivalents	727	307	347		386
Restricted cash and securities	1	1
Receivables, less allowances for doubtful accounts	47	34
Due from affiliates	0	0
Other	56	45
Total Current Assets	831	387
Property, Plant and Equipment, net	3,423	3,152
Restricted Cash and Securities	14	16
Goodwill and Other Intangibles Assets, net	363	373
Investment in Subsidiaries	3,734	3,729
Deferred Tax Assets	0	0
Other Assets, net	12	9
Total Assets	8,377	7,666
Liabilities:
Accounts payable	195	215
Current portion of long-term debt	2	3
Accrued payroll and employee benefits	186	174
Accrued interest	0	0
Current portion of deferred revenue	119	118
Due to affiliates	37,990	34,401
Other	115	62
Total Current Liabilities	38,607	34,973
Long-Term Debt, less current portion	15	16
Deferred Revenue, less current portion	680	617
Other Liabilities	133	125
Stockholders' Equity (Deficit)	(31,058)	(28,065)
Total Liabilities and Stockholders’ Equity	8,377	7,666
Other Non-Guarantor Subsidiaries
Current Assets:
Cash and cash equivalents	109	261	270		335
Restricted cash and securities	7	6
Receivables, less allowances for doubtful accounts	710	703
Due from affiliates	2,816	0
Other	55	89
Total Current Assets	3,697	1,059
Property, Plant and Equipment, net	6,455	6,708
Restricted Cash and Securities	1	1
Goodwill and Other Intangibles Assets, net	8,513	8,730
Investment in Subsidiaries	0	0
Deferred Tax Assets	556	300
Other Assets, net	39	17
Total Assets	19,261	16,815
Liabilities:
Accounts payable	433	449
Current portion of long-term debt	13	13
Accrued payroll and employee benefits	32	99
Accrued interest	7	4
Current portion of deferred revenue	148	169
Due to affiliates	0	1,391
Other	64	95
Total Current Liabilities	697	2,220
Long-Term Debt, less current portion	169	175
Deferred Revenue, less current portion	297	304
Other Liabilities	484	608
Stockholders' Equity (Deficit)	17,614	13,508
Total Liabilities and Stockholders’ Equity	19,261	16,815
Eliminations
Current Assets:
Cash and cash equivalents	0	0	$ 0		$ 0
Restricted cash and securities	0	0
Receivables, less allowances for doubtful accounts	0	0
Due from affiliates	(37,990)	(35,792)
Other	0	0
Total Current Assets	(37,990)	(35,792)
Property, Plant and Equipment, net	0	0
Restricted Cash and Securities	0	0
Goodwill and Other Intangibles Assets, net	0	0
Investment in Subsidiaries	(38,220)	(35,192)
Deferred Tax Assets	0	0
Other Assets, net	0	0
Total Assets	(76,210)	(70,984)
Liabilities:
Accounts payable	0	0
Current portion of long-term debt	0	0
Accrued payroll and employee benefits	0	0
Accrued interest	0	0
Current portion of deferred revenue	0	0
Due to affiliates	(37,990)	(35,792)
Other	0	0
Total Current Liabilities	(37,990)	(35,792)
Long-Term Debt, less current portion	0	0
Deferred Revenue, less current portion	0	0
Other Liabilities	0	0
Stockholders' Equity (Deficit)	(38,220)	(35,192)
Total Liabilities and Stockholders’ Equity	$ (76,210)	$ (70,984)