Condensed Consolidating Financial Information - Balance Sheets (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Current Assets:
Cash and cash equivalents	$ 979	$ 918	$ 616	$ 836
Restricted cash and securities	8	10
Receivables, less allowances for doubtful accounts	714	648
Due from affiliates	0	0
Other	141	131
Total Current Assets	1,842	1,707
Property, Plant and Equipment, net	8,199	8,136
Restricted Cash and Securities	35	51
Goodwill and Other Intangibles Assets, net	2,833	2,899
Investment in Subsidiaries	0	0
Other Assets, net	398	395
Total Assets	13,307	13,188
Current Liabilities:
Accounts payable	779	747
Current portion of long-term debt	216	65
Accrued payroll and employee benefits	211	209
Accrued interest	209	216
Current portion of deferred revenue	251	264
Due to affiliates	0	0
Other	136	157
Total Current Liabilities	1,802	1,658
Long-Term Debt, less current portion	8,516	8,385
Deferred Revenue, less current portion	887	885
Other Liabilities	931	1,067
Commitments and Contingencies	0	0
Stockholders' Equity (Deficit)	1,171	1,193	(157)	491
Total Liabilities and Stockholders’ Equity	13,307	13,188
Level 3 Communications, Inc.
Current Assets:
Cash and cash equivalents	253	2	173	236
Restricted cash and securities	0	0
Receivables, less allowances for doubtful accounts	0	0
Due from affiliates	14,446	13,472
Other	3	3
Total Current Assets	14,702	13,477
Property, Plant and Equipment, net	0	0
Restricted Cash and Securities	12	18
Goodwill and Other Intangibles Assets, net	0	0
Investment in Subsidiaries	(11,756)	(10,718)
Other Assets, net	16	13
Total Assets	2,974	2,790
Current Liabilities:
Accounts payable	1	0
Current portion of long-term debt	172	0
Accrued payroll and employee benefits	0	0
Accrued interest	45	50
Current portion of deferred revenue	0	0
Due to affiliates	0	0
Other	1	0
Total Current Liabilities	219	50
Long-Term Debt, less current portion	1,570	1,533
Deferred Revenue, less current portion	0	0
Other Liabilities	14	14
Stockholders' Equity (Deficit)	1,171	1,193
Total Liabilities and Stockholders’ Equity	2,974	2,790
Level 3 Financing, Inc.
Current Assets:
Cash and cash equivalents	5	6	7	8
Restricted cash and securities	0	0
Receivables, less allowances for doubtful accounts	0	0
Due from affiliates	15,709	14,584
Other	16	16
Total Current Assets	15,730	14,606
Property, Plant and Equipment, net	0	0
Restricted Cash and Securities	0	0
Goodwill and Other Intangibles Assets, net	0	0
Investment in Subsidiaries	(20,470)	(18,467)
Other Assets, net	119	109
Total Assets	(4,621)	(3,752)
Current Liabilities:
Accounts payable	2	0
Current portion of long-term debt	6	0
Accrued payroll and employee benefits	0	0
Accrued interest	163	165
Current portion of deferred revenue	0	0
Due to affiliates	0	0
Other	1	1
Total Current Liabilities	172	166
Long-Term Debt, less current portion	6,886	6,688
Deferred Revenue, less current portion	0	0
Other Liabilities	81	116
Stockholders' Equity (Deficit)	(11,760)	(10,722)
Total Liabilities and Stockholders’ Equity	(4,621)	(3,752)
Level 3 Communications, LLC
Current Assets:
Cash and cash equivalents	386	618	350	431
Restricted cash and securities	1	1
Receivables, less allowances for doubtful accounts	93	59
Due from affiliates	0	0
Other	49	48
Total Current Assets	529	726
Property, Plant and Equipment, net	2,926	2,823
Restricted Cash and Securities	17	19
Goodwill and Other Intangibles Assets, net	429	481
Investment in Subsidiaries	3,242	3,412
Other Assets, net	11	6
Total Assets	7,154	7,467
Current Liabilities:
Accounts payable	53	37
Current portion of long-term debt	6	2
Accrued payroll and employee benefits	161	116
Accrued interest	0	0
Current portion of deferred revenue	109	107
Due to affiliates	30,162	28,092
Other	29	52
Total Current Liabilities	30,520	28,406
Long-Term Debt, less current portion	20	22
Deferred Revenue, less current portion	602	612
Other Liabilities	75	146
Stockholders' Equity (Deficit)	(24,063)	(21,719)
Total Liabilities and Stockholders’ Equity	7,154	7,467
Other Non-Guarantor Subsidiaries
Current Assets:
Cash and cash equivalents	335	292	86	161
Restricted cash and securities	7	9
Receivables, less allowances for doubtful accounts	621	589
Due from affiliates	7	36
Other	73	64
Total Current Assets	1,043	990
Property, Plant and Equipment, net	5,273	5,313
Restricted Cash and Securities	6	14
Goodwill and Other Intangibles Assets, net	2,404	2,418
Investment in Subsidiaries	0	0
Other Assets, net	252	267
Total Assets	8,978	9,002
Current Liabilities:
Accounts payable	723	710
Current portion of long-term debt	32	63
Accrued payroll and employee benefits	50	93
Accrued interest	1	1
Current portion of deferred revenue	142	157
Due to affiliates	0	0
Other	105	104
Total Current Liabilities	1,053	1,128
Long-Term Debt, less current portion	40	142
Deferred Revenue, less current portion	285	273
Other Liabilities	761	791
Stockholders' Equity (Deficit)	6,839	6,668
Total Liabilities and Stockholders’ Equity	8,978	9,002
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	(30,162)	(28,092)
Other	0	0
Total Current Assets	(30,162)	(28,092)
Property, Plant and Equipment, net	0	0
Restricted Cash and Securities	0	0
Goodwill and Other Intangibles Assets, net	0	0
Investment in Subsidiaries	28,984	25,773
Other Assets, net	0	0
Total Assets	(1,178)	(2,319)
Current 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	(30,162)	(28,092)
Other	0	0
Total Current Liabilities	(30,162)	(28,092)
Long-Term Debt, less current portion	0	0
Deferred Revenue, less current portion	0	0
Other Liabilities	0	0
Stockholders' Equity (Deficit)	28,984	25,773
Total Liabilities and Stockholders’ Equity	$ (1,178)	$ (2,319)