Condensed Consolidating Financial Information - Balance Sheets (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2011
Current Assets:
Cash and cash equivalents	$ 596	$ 979	$ 733	$ 918
Restricted cash and securities	7	8
Receivables, less allowances for doubtful accounts	721	714
Due from affiliates	0	0
Other	179	141
Total Current Assets	1,503	1,842
Property, Plant and Equipment, net	8,171	8,199
Restricted Cash and Securities	27	35
Goodwill and Other Intangibles Assets, net	2,797	2,833
Investment in Subsidiaries	0	0
Other Assets, net	367	398
Total Assets	12,865	13,307
Liabilities and Stockholders' Equity:
Accounts payable	688	779
Current portion of long-term debt	30	216
Accrued payroll and employee benefits	177	211
Accrued interest	192	209
Current portion of deferred revenue	226	251
Due to affiliates	0	0
Other	190	136
Total Current Liabilities	1,503	1,802
Long-Term Debt, less current portion	8,506	8,516
Deferred Revenue, less current portion	906	887
Other Liabilities	842	931
Commitments and Contingencies	0	0
Stockholders' Equity (Deficit)	1,108	1,171
Total Liabilities and Stockholders’ Equity (Deficit)	12,865	13,307
Level 3 Communications, Inc.
Current Assets:
Cash and cash equivalents	9	253	2	2
Restricted cash and securities	0	0
Receivables, less allowances for doubtful accounts	0	0
Due from affiliates	15,017	14,446
Other	4	3
Total Current Assets	15,030	14,702
Property, Plant and Equipment, net	0	0
Restricted Cash and Securities	7	12
Goodwill and Other Intangibles Assets, net	0	0
Investment in Subsidiaries	(12,322)	(11,756)
Other Assets, net	14	16
Total Assets	2,729	2,974
Liabilities and Stockholders' Equity:
Accounts payable	1	1
Current portion of long-term debt	0	172
Accrued payroll and employee benefits	0	0
Accrued interest	33	45
Current portion of deferred revenue	0	0
Due to affiliates	0	0
Other	1	1
Total Current Liabilities	35	219
Long-Term Debt, less current portion	1,571	1,570
Deferred Revenue, less current portion	0	0
Other Liabilities	15	14
Commitments and Contingencies	0
Stockholders' Equity (Deficit)	1,108	1,171
Total Liabilities and Stockholders’ Equity (Deficit)	2,729	2,974
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	16,312	15,709
Other	16	16
Total Current Assets	16,333	15,730
Property, Plant and Equipment, net	0	0
Restricted Cash and Securities	0	0
Goodwill and Other Intangibles Assets, net	0	0
Investment in Subsidiaries	(21,656)	(20,470)
Other Assets, net	110	119
Total Assets	(5,213)	(4,621)
Liabilities and Stockholders' Equity:
Accounts payable	1	2
Current portion of long-term debt	6	6
Accrued payroll and employee benefits	0	0
Accrued interest	158	163
Current portion of deferred revenue	0	0
Due to affiliates	0	0
Other	36	1
Total Current Liabilities	201	172
Long-Term Debt, less current portion	6,886	6,886
Deferred Revenue, less current portion	0	0
Other Liabilities	26	81
Commitments and Contingencies	0
Stockholders' Equity (Deficit)	(12,326)	(11,760)
Total Liabilities and Stockholders’ Equity (Deficit)	(5,213)	(4,621)
Level 3 Communications, LLC
Current Assets:
Cash and cash equivalents	357	386	416	618
Restricted cash and securities	1	1
Receivables, less allowances for doubtful accounts	103	93
Due from affiliates	0	0
Other	67	49
Total Current Assets	528	529
Property, Plant and Equipment, net	2,970	2,926
Restricted Cash and Securities	17	17
Goodwill and Other Intangibles Assets, net	412	429
Investment in Subsidiaries	4,358	3,242
Other Assets, net	11	11
Total Assets	8,296	7,154
Liabilities and Stockholders' Equity:
Accounts payable	42	53
Current portion of long-term debt	3	6
Accrued payroll and employee benefits	131	161
Accrued interest	0	0
Current portion of deferred revenue	106	109
Due to affiliates	31,035	30,162
Other	48	29
Total Current Liabilities	31,365	30,520
Long-Term Debt, less current portion	18	20
Deferred Revenue, less current portion	593	602
Other Liabilities	23	75
Commitments and Contingencies	0
Stockholders' Equity (Deficit)	(23,703)	(24,063)
Total Liabilities and Stockholders’ Equity (Deficit)	8,296	7,154
Other Non-Guarantor Subsidiaries
Current Assets:
Cash and cash equivalents	225	335	309	292
Restricted cash and securities	6	7
Receivables, less allowances for doubtful accounts	618	621
Due from affiliates	0	7
Other	92	73
Total Current Assets	941	1,043
Property, Plant and Equipment, net	5,201	5,273
Restricted Cash and Securities	3	6
Goodwill and Other Intangibles Assets, net	2,385	2,404
Investment in Subsidiaries	0	0
Other Assets, net	232	252
Total Assets	8,762	8,978
Liabilities and Stockholders' Equity:
Accounts payable	644	723
Current portion of long-term debt	21	32
Accrued payroll and employee benefits	46	50
Accrued interest	1	1
Current portion of deferred revenue	120	142
Due to affiliates	294	0
Other	105	105
Total Current Liabilities	1,231	1,053
Long-Term Debt, less current portion	31	40
Deferred Revenue, less current portion	313	285
Other Liabilities	778	761
Commitments and Contingencies	0
Stockholders' Equity (Deficit)	6,409	6,839
Total Liabilities and Stockholders’ Equity (Deficit)	8,762	8,978
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	(31,329)	(30,162)
Other	0	0
Total Current Assets	(31,329)	(30,162)
Property, Plant and Equipment, net	0	0
Restricted Cash and Securities	0	0
Goodwill and Other Intangibles Assets, net	0	0
Investment in Subsidiaries	29,620	28,984
Other Assets, net	0	0
Total Assets	(1,709)	(1,178)
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	(31,329)	(30,162)
Other	0	0
Total Current Liabilities	(31,329)	(30,162)
Long-Term Debt, less current portion	0	0
Deferred Revenue, less current portion	0	0
Other Liabilities	0	0
Commitments and Contingencies	0
Stockholders' Equity (Deficit)	29,620	28,984
Total Liabilities and Stockholders’ Equity (Deficit)	$ (1,709)	$ (1,178)