Condensed Consolidating Financial Information - Balance Sheets (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Current Assets:
Cash and cash equivalents	$ 1,114	$ 580	$ 607	$ 631
Restricted cash and securities	7	7
Receivables, less allowances for doubtful accounts	743	737
Due from affiliates	0	0
Other	188	165
Total Current Assets	2,052	1,489
Property, Plant and Equipment, net	9,744	9,860
Restricted Cash and Securities	19	20
Goodwill and Other Intangibles Assets, net	9,038	9,103
Investment in Subsidiaries	0	0
Other Assets, net	450	475
Total Assets	21,303	20,947
Liabilities and Stockholders' Equity:
Accounts payable	629	664
Current portion of long-term debt	510	349
Accrued payroll and employee benefits	177	273
Accrued interest	187	174
Current portion of deferred revenue	300	287
Due to affiliates	0	0
Other	150	167
Total Current Liabilities	1,953	1,914
Long-Term Debt, less current portion	10,990	10,984
Deferred Revenue, less current portion	895	921
Other Liabilities	748	765
Commitments and Contingencies
Stockholders' Equity (Deficit)	6,717	6,363
Total Liabilities and Stockholders’ Equity (Deficit)	21,303	20,947
Level 3 Communications, Inc.
Current Assets:
Cash and cash equivalents	14	7	8	8
Restricted cash and securities	0	0
Receivables, less allowances for doubtful accounts	0	0
Due from affiliates	14,987	14,522
Other	2	2
Total Current Assets	15,003	14,531
Property, Plant and Equipment, net	0	0
Restricted Cash and Securities	3	3
Goodwill and Other Intangibles Assets, net	0	0
Investment in Subsidiaries	16,700	16,686
Other Assets, net	25	28
Total Assets	31,731	31,248
Liabilities and Stockholders' Equity:
Accounts payable	0	0
Current portion of long-term debt	0	333
Accrued payroll and employee benefits	0	0
Accrued interest	12	12
Current portion of deferred revenue	0	0
Due to affiliates	0	0
Other	0	0
Total Current Liabilities	12	345
Long-Term Debt, less current portion	900	900
Deferred Revenue, less current portion	0	0
Other Liabilities	15	16
Commitments and Contingencies
Stockholders' Equity (Deficit)	30,804	29,987
Total Liabilities and Stockholders’ Equity (Deficit)	31,731	31,248
Level 3 Financing, Inc.
Current Assets:
Cash and cash equivalents	5	5	6	6
Restricted cash and securities	0	0
Receivables, less allowances for doubtful accounts	0	0
Due from affiliates	22,125	21,270
Other	27	21
Total Current Assets	22,157	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	14,342	14,777
Other Assets, net	126	129
Total Assets	36,625	36,202
Liabilities and Stockholders' Equity:
Accounts payable	0	0
Current portion of long-term debt	494	0
Accrued payroll and employee benefits	0	0
Accrued interest	170	158
Current portion of deferred revenue	0	0
Due to affiliates	0	0
Other	2	2
Total Current Liabilities	666	160
Long-Term Debt, less current portion	9,900	9,893
Deferred Revenue, less current portion	0	0
Other Liabilities	24	24
Commitments and Contingencies
Stockholders' Equity (Deficit)	26,035	26,125
Total Liabilities and Stockholders’ Equity (Deficit)	36,625	36,202
Level 3 Communications, LLC
Current Assets:
Cash and cash equivalents	841	307	356	347
Restricted cash and securities	1	1
Receivables, less allowances for doubtful accounts	41	34
Due from affiliates	0	0
Other	70	45
Total Current Assets	953	387
Property, Plant and Equipment, net	3,181	3,152
Restricted Cash and Securities	15	16
Goodwill and Other Intangibles Assets, net	371	373
Investment in Subsidiaries	3,726	3,729
Other Assets, net	9	9
Total Assets	8,255	7,666
Liabilities and Stockholders' Equity:
Accounts payable	225	215
Current portion of long-term debt	3	3
Accrued payroll and employee benefits	135	174
Accrued interest	0	0
Current portion of deferred revenue	114	118
Due to affiliates	35,463	34,401
Other	82	62
Total Current Liabilities	36,022	34,973
Long-Term Debt, less current portion	16	16
Deferred Revenue, less current portion	599	617
Other Liabilities	127	125
Commitments and Contingencies
Stockholders' Equity (Deficit)	(28,509)	(28,065)
Total Liabilities and Stockholders’ Equity (Deficit)	8,255	7,666
Other Non-Guarantor Subsidiaries
Current Assets:
Cash and cash equivalents	254	261	237	270
Restricted cash and securities	6	6
Receivables, less allowances for doubtful accounts	702	703
Due from affiliates	0	0
Other	89	97
Total Current Assets	1,051	1,067
Property, Plant and Equipment, net	6,563	6,708
Restricted Cash and Securities	1	1
Goodwill and Other Intangibles Assets, net	8,667	8,730
Investment in Subsidiaries	0	0
Other Assets, net	290	309
Total Assets	16,572	16,815
Liabilities and Stockholders' Equity:
Accounts payable	404	449
Current portion of long-term debt	13	13
Accrued payroll and employee benefits	42	99
Accrued interest	5	4
Current portion of deferred revenue	186	169
Due to affiliates	1,649	1,391
Other	66	103
Total Current Liabilities	2,365	2,228
Long-Term Debt, less current portion	174	175
Deferred Revenue, less current portion	296	304
Other Liabilities	582	600
Commitments and Contingencies
Stockholders' Equity (Deficit)	13,155	13,508
Total Liabilities and Stockholders’ Equity (Deficit)	16,572	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	(37,112)	(35,792)
Other	0	0
Total Current Assets	(37,112)	(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	(34,768)	(35,192)
Other Assets, net	0	0
Total Assets	(71,880)	(70,984)
Liabilities and Stockholders' Equity:
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	(37,112)	(35,792)
Other	0	0
Total Current Liabilities	(37,112)	(35,792)
Long-Term Debt, less current portion	0	0
Deferred Revenue, less current portion	0	0
Other Liabilities	0	0
Commitments and Contingencies
Stockholders' Equity (Deficit)	(34,768)	(35,192)
Total Liabilities and Stockholders’ Equity (Deficit)	$ (71,880)	$ (70,984)