Condensed Consolidating Financial Information - Balance Sheets (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 01, 2012	Dec. 31, 2011	Dec. 31, 2010
Current Assets:
Cash and cash equivalents	$ 580	$ 631	$ 979		$ 918	$ 918
Restricted cash and securities	7	7
Receivables, less allowances for doubtful accounts	737	673
Due from affiliates	0	0
Other	165	143
Total Current Assets	1,489	1,454
Property, Plant and Equipment, net	9,860	8,240
Restricted Cash and Securities	20	23
Goodwill and Other Intangibles Assets, net	9,103	2,782
Investment in Subsidiaries	0	0
Other Assets, net	475	375
Total Assets	20,947	12,874
Liabilities:
Accounts payable	664	625
Current portion of long-term debt	349	31
Accrued payroll and employee benefits	273	209
Accrued interest	174	160
Current portion of deferred revenue	287	253
Due to affiliates	0	0
Other	167	168
Total Current Liabilities	1,914	1,446
Long-Term Debt, less current portion	10,984	8,331
Deferred Revenue, less current portion	921	906
Other Liabilities	765	780
Commitments and Contingencies	0	0
Stockholders' Equity (Deficit)	6,363	1,411	1,171	1,193
Total Liabilities and Stockholders’ Equity	20,947	12,874
Level 3 Communications, Inc.
Current Assets:
Cash and cash equivalents	7	8	253			2
Restricted cash and securities	0	0
Receivables, less allowances for doubtful accounts	0	0
Due from affiliates	14,522	15,507
Other	2	2
Total Current Assets	14,531	15,517
Property, Plant and Equipment, net	0	0
Restricted Cash and Securities	3	3
Goodwill and Other Intangibles Assets, net	0	0
Investment in Subsidiaries	16,686	10,039
Other Assets, net	28	10
Total Assets	31,248	25,569
Liabilities:
Accounts payable	0	0
Current portion of long-term debt	333	0
Accrued payroll and employee benefits	0	0
Accrued interest	12	30
Current portion of deferred revenue	0	0
Due to affiliates	0	0
Other	0	0
Total Current Liabilities	345	30
Long-Term Debt, less current portion	900	1,370
Deferred Revenue, less current portion	0	0
Other Liabilities	16	15
Stockholders' Equity (Deficit)	29,987	24,154
Total Liabilities and Stockholders’ Equity	31,248	25,569
Level 3 Financing, Inc.
Current Assets:
Cash and cash equivalents	5	6	5			6
Restricted cash and securities	0	0
Receivables, less allowances for doubtful accounts	0	0
Due from affiliates	21,270	16,886
Other	21	15
Total Current Assets	21,296	16,907
Property, Plant and Equipment, net	0	0
Restricted Cash and Securities	0	0
Goodwill and Other Intangibles Assets, net	0	0
Investment in Subsidiaries	14,777	27,014
Other Assets, net	129	113
Total Assets	36,202	44,034
Liabilities:
Accounts payable	0	2
Current portion of long-term debt	0	0
Accrued payroll and employee benefits	0	0
Accrued interest	158	129
Current portion of deferred revenue	0	0
Due to affiliates	0	0
Other	2	13
Total Current Liabilities	160	144
Long-Term Debt, less current portion	9,893	6,905
Deferred Revenue, less current portion	0	0
Other Liabilities	24	27
Stockholders' Equity (Deficit)	26,125	36,958
Total Liabilities and Stockholders’ Equity	36,202	44,034
Level 3 Communications, LLC
Current Assets:
Cash and cash equivalents	307	347	386			618
Restricted cash and securities	1	1
Receivables, less allowances for doubtful accounts	34	79
Due from affiliates	0	0
Other	45	47
Total Current Assets	387	474
Property, Plant and Equipment, net	3,152	3,028
Restricted Cash and Securities	16	18
Goodwill and Other Intangibles Assets, net	373	395
Investment in Subsidiaries	3,729	3,735
Other Assets, net	9	11
Total Assets	7,666	7,661
Liabilities:
Accounts payable	215	42
Current portion of long-term debt	3	3
Accrued payroll and employee benefits	174	171
Accrued interest	0	0
Current portion of deferred revenue	118	131
Due to affiliates	34,401	32,165
Other	62	74
Total Current Liabilities	34,973	32,586
Long-Term Debt, less current portion	16	17
Deferred Revenue, less current portion	617	603
Other Liabilities	125	135
Stockholders' Equity (Deficit)	(28,065)	(25,680)
Total Liabilities and Stockholders’ Equity	7,666	7,661
Other Non-Guarantor Subsidiaries
Current Assets:
Cash and cash equivalents	261	270	335			292
Restricted cash and securities	6	6
Receivables, less allowances for doubtful accounts	703	594
Due from affiliates	0	0
Other	97	79
Total Current Assets	1,067	949
Property, Plant and Equipment, net	6,708	5,212
Restricted Cash and Securities	1	2
Goodwill and Other Intangibles Assets, net	8,730	2,387
Investment in Subsidiaries	0	0
Other Assets, net	309	241
Total Assets	16,815	8,791
Liabilities:
Accounts payable	449	581
Current portion of long-term debt	13	28
Accrued payroll and employee benefits	99	38
Accrued interest	4	1
Current portion of deferred revenue	169	122
Due to affiliates	1,391	228
Other	103	81
Total Current Liabilities	2,228	1,079
Long-Term Debt, less current portion	175	39
Deferred Revenue, less current portion	304	303
Other Liabilities	600	603
Stockholders' Equity (Deficit)	13,508	6,767
Total Liabilities and Stockholders’ Equity	16,815	8,791
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	(35,792)	(32,393)
Other	0	0
Total Current Assets	(35,792)	(32,393)
Property, Plant and Equipment, net	0	0
Restricted Cash and Securities	0	0
Goodwill and Other Intangibles Assets, net	0	0
Investment in Subsidiaries	(35,192)	(40,788)
Other Assets, net	0	0
Total Assets	(70,984)	(73,181)
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	(35,792)	(32,393)
Other	0	0
Total Current Liabilities	(35,792)	(32,393)
Long-Term Debt, less current portion	0	0
Deferred Revenue, less current portion	0	0
Other Liabilities	0	0
Stockholders' Equity (Deficit)	(35,192)	(40,788)
Total Liabilities and Stockholders’ Equity	$ (70,984)	$ (73,181)