Condensed Consolidating Financial Information - Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current Assets:
Cash and cash equivalents	$ 1,819	$ 854	$ 580	$ 631
Restricted cash and securities	7	8
Receivables, less allowances for doubtful accounts	712	757
Due from affiliates	0	0
Other	115	111
Total Current Assets	2,653	1,730
Property, Plant and Equipment, net	10,139	9,878
Restricted Cash and Securities	31	42
Goodwill and Other Intangibles Assets, net	8,644	8,876
Investment in Subsidiaries	0	0
Deferred Tax Assets	3,370	3,441
Other Assets, net	51	50
Total Assets	24,888	24,017
Liabilities:
Accounts payable	706	629
Current portion of long-term debt	7	15
Accrued payroll and employee benefits	195	218
Accrued interest	129	108
Current portion of deferred revenue	266	267
Due to affiliates	0	0
Other	168	179
Total Current Liabilities	1,471	1,416
Long-Term Debt, less current portion	10,877	10,866
Deferred Revenue, less current portion	1,001	977
Other Liabilities	622	632
Commitments and Contingencies	0	0
Stockholders' Equity (Deficit)	10,917	10,126	6,363	1,411
Total Liabilities and Stockholders’ Equity	24,888	24,017
Level 3 Communications, Inc.
Current Assets:
Cash and cash equivalents	15	12	7	8
Restricted cash and securities	0	0
Receivables, less allowances for doubtful accounts	0	0
Due from affiliates	17,032	12,415
Other	0	0
Total Current Assets	17,047	12,427
Property, Plant and Equipment, net	0	0
Restricted Cash and Securities	22	27
Goodwill and Other Intangibles Assets, net	0	0
Investment in Subsidiaries	16,869	16,772
Deferred Tax Assets	51	38
Other Assets, net	0	0
Total Assets	33,989	29,264
Liabilities:
Accounts payable	0	0
Current portion of long-term debt	0	0
Accrued payroll and employee benefits	0	0
Accrued interest	11	11
Current portion of deferred revenue	0	0
Due to affiliates	0	0
Other	0	0
Total Current Liabilities	11	11
Long-Term Debt, less current portion	592	591
Deferred Revenue, less current portion	0	0
Other Liabilities	16	15
Stockholders' Equity (Deficit)	33,370	28,647
Total Liabilities and Stockholders’ Equity	33,989	29,264
Level 3 Financing, Inc.
Current Assets:
Cash and cash equivalents	0	6	5	6
Restricted cash and securities	0	0
Receivables, less allowances for doubtful accounts	0	0
Due from affiliates	21,715	22,759
Other	0	0
Total Current Assets	21,715	22,765
Property, Plant and Equipment, net	0	0
Restricted Cash and Securities	0	0
Goodwill and Other Intangibles Assets, net	0	0
Investment in Subsidiaries	17,599	17,714
Deferred Tax Assets	2,687	2,847
Other Assets, net	0	0
Total Assets	42,001	43,326
Liabilities:
Accounts payable	0	1
Current portion of long-term debt	0	0
Accrued payroll and employee benefits	0	0
Accrued interest	110	90
Current portion of deferred revenue	0	0
Due to affiliates	0	0
Other	0	0
Total Current Liabilities	110	91
Long-Term Debt, less current portion	10,108	10,092
Deferred Revenue, less current portion	0	0
Other Liabilities	0	0
Stockholders' Equity (Deficit)	31,783	33,143
Total Liabilities and Stockholders’ Equity	42,001	43,326
Level 3 Communications, LLC
Current Assets:
Cash and cash equivalents	1,700	727	307	347
Restricted cash and securities	1	1
Receivables, less allowances for doubtful accounts	26	47
Due from affiliates	0	0
Other	87	56
Total Current Assets	1,814	831
Property, Plant and Equipment, net	3,869	3,423
Restricted Cash and Securities	9	14
Goodwill and Other Intangibles Assets, net	353	363
Investment in Subsidiaries	3,674	3,734
Deferred Tax Assets	0	0
Other Assets, net	16	12
Total Assets	9,735	8,377
Liabilities:
Accounts payable	307	195
Current portion of long-term debt	2	2
Accrued payroll and employee benefits	160	186
Accrued interest	0	0
Current portion of deferred revenue	116	119
Due to affiliates	40,927	37,990
Other	127	115
Total Current Liabilities	41,639	38,607
Long-Term Debt, less current portion	13	15
Deferred Revenue, less current portion	719	680
Other Liabilities	155	133
Stockholders' Equity (Deficit)	(32,791)	(31,058)
Total Liabilities and Stockholders’ Equity	9,735	8,377
Other Non-Guarantor Subsidiaries
Current Assets:
Cash and cash equivalents	104	109	261	270
Restricted cash and securities	6	7
Receivables, less allowances for doubtful accounts	686	710
Due from affiliates	2,180	2,816
Other	28	55
Total Current Assets	3,004	3,697
Property, Plant and Equipment, net	6,270	6,455
Restricted Cash and Securities	0	1
Goodwill and Other Intangibles Assets, net	8,291	8,513
Investment in Subsidiaries	0	0
Deferred Tax Assets	632	556
Other Assets, net	35	38
Total Assets	18,232	19,260
Liabilities:
Accounts payable	399	433
Current portion of long-term debt	5	13
Accrued payroll and employee benefits	35	32
Accrued interest	8	7
Current portion of deferred revenue	150	148
Due to affiliates	0	0
Other	41	64
Total Current Liabilities	638	697
Long-Term Debt, less current portion	164	168
Deferred Revenue, less current portion	282	297
Other Liabilities	451	484
Stockholders' Equity (Deficit)	16,697	17,614
Total Liabilities and Stockholders’ Equity	18,232	19,260
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	(40,927)	(37,990)
Other	0	0
Total Current Assets	(40,927)	(37,990)
Property, Plant and Equipment, net	0	0
Restricted Cash and Securities	0	0
Goodwill and Other Intangibles Assets, net	0	0
Investment in Subsidiaries	(38,142)	(38,220)
Deferred Tax Assets	0	0
Other Assets, net	0	0
Total Assets	(79,069)	(76,210)
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	(40,927)	(37,990)
Other	0	0
Total Current Liabilities	(40,927)	(37,990)
Long-Term Debt, less current portion	0	0
Deferred Revenue, less current portion	0	0
Other Liabilities	0	0
Stockholders' Equity (Deficit)	(38,142)	(38,220)
Total Liabilities and Stockholders’ Equity	$ (79,069)	$ (76,210)