Condensed Consolidating Financial Information - Balance Sheets (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
Current Assets:
Cash and cash equivalents	$ 549	$ 580	$ 637	$ 631
Restricted cash and securities	8	7
Receivables, less allowances for doubtful accounts	756	737
Due from affiliates	0	0
Other	190	165
Total Current Assets	1,503	1,489
Property, Plant and Equipment, net	9,900	9,860
Restricted Cash and Securities	43	20
Goodwill and Other Intangibles Assets, net	8,987	9,103
Investment in Subsidiaries	0	0
Other Assets, net	451	475
Total Assets	20,884	20,947
Liabilities and Stockholders' Equity:
Accounts payable	637	664
Current portion of long-term debt	17	349
Accrued payroll and employee benefits	202	273
Accrued interest	125	174
Current portion of deferred revenue	280	287
Due to affiliates	0	0
Other	179	167
Total Current Liabilities	1,440	1,914
Long-Term Debt, less current portion	11,001	10,984
Deferred Revenue, less current portion	892	921
Other Liabilities	$ 734	$ 765
Commitments and Contingencies
Stockholders' Equity (Deficit)	$ 6,817	$ 6,363
Total Liabilities and Stockholders’ Equity (Deficit)	20,884	20,947
Level 3 Communications, Inc.
Current Assets:
Cash and cash equivalents	13	7	8	8
Restricted cash and securities	0	0
Receivables, less allowances for doubtful accounts	0	0
Due from affiliates	14,988	14,522
Other	1	2
Total Current Assets	15,002	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	16,716	16,686
Other Assets, net	21	28
Total Assets	31,766	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	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
Commitments and Contingencies
Stockholders' Equity (Deficit)	$ 31,140	$ 29,987
Total Liabilities and Stockholders’ Equity (Deficit)	31,766	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	22,096	21,270
Other	18	21
Total Current Assets	22,119	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	14,580	14,777
Other Assets, net	124	129
Total Assets	36,823	36,202
Liabilities and Stockholders' Equity:
Accounts payable	2	0
Current portion of long-term debt	0	0
Accrued payroll and employee benefits	0	0
Accrued interest	108	158
Current portion of deferred revenue	0	0
Due to affiliates	0	0
Other	1	2
Total Current Liabilities	111	160
Long-Term Debt, less current portion	10,209	9,893
Deferred Revenue, less current portion	0	0
Other Liabilities	$ 24	$ 24
Commitments and Contingencies
Stockholders' Equity (Deficit)	$ 26,479	$ 26,125
Total Liabilities and Stockholders’ Equity (Deficit)	36,823	36,202
Level 3 Communications, LLC
Current Assets:
Cash and cash equivalents	289	307	414	347
Restricted cash and securities	1	1
Receivables, less allowances for doubtful accounts	32	34
Due from affiliates	0	0
Other	77	45
Total Current Assets	399	387
Property, Plant and Equipment, net	3,235	3,152
Restricted Cash and Securities	15	16
Goodwill and Other Intangibles Assets, net	368	373
Investment in Subsidiaries	3,724	3,729
Other Assets, net	11	9
Total Assets	7,752	7,666
Liabilities and Stockholders' Equity:
Accounts payable	219	215
Current portion of long-term debt	3	3
Accrued payroll and employee benefits	165	174
Accrued interest	0	0
Current portion of deferred revenue	106	118
Due to affiliates	35,781	34,401
Other	86	62
Total Current Liabilities	36,360	34,973
Long-Term Debt, less current portion	16	16
Deferred Revenue, less current portion	595	617
Other Liabilities	$ 125	$ 125
Commitments and Contingencies
Stockholders' Equity (Deficit)	$ (29,344)	$ (28,065)
Total Liabilities and Stockholders’ Equity (Deficit)	7,752	7,666
Other Non-Guarantor Subsidiaries
Current Assets:
Cash and cash equivalents	242	261	209	270
Restricted cash and securities	7	6
Receivables, less allowances for doubtful accounts	724	703
Due from affiliates	0	0
Other	94	97
Total Current Assets	1,067	1,067
Property, Plant and Equipment, net	6,665	6,708
Restricted Cash and Securities	1	1
Goodwill and Other Intangibles Assets, net	8,619	8,730
Investment in Subsidiaries	0	0
Other Assets, net	295	309
Total Assets	16,647	16,815
Liabilities and Stockholders' Equity:
Accounts payable	416	449
Current portion of long-term debt	14	13
Accrued payroll and employee benefits	37	99
Accrued interest	6	4
Current portion of deferred revenue	174	169
Due to affiliates	1,303	1,391
Other	92	103
Total Current Liabilities	2,042	2,228
Long-Term Debt, less current portion	176	175
Deferred Revenue, less current portion	297	304
Other Liabilities	$ 570	$ 600
Commitments and Contingencies
Stockholders' Equity (Deficit)	$ 13,562	$ 13,508
Total Liabilities and Stockholders’ Equity (Deficit)	16,647	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	(37,084)	(35,792)
Other	0	0
Total Current Assets	(37,084)	(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	(35,020)	(35,192)
Other Assets, net	0	0
Total Assets	(72,104)	(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	(37,084)	(35,792)
Other	0	0
Total Current Liabilities	(37,084)	(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)	$ (35,020)	$ (35,192)
Total Liabilities and Stockholders’ Equity (Deficit)	$ (72,104)	$ (70,984)