Condensed Consolidating Financial Information - Balance Sheets (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011
Current Assets:
Cash and cash equivalents	$ 610	$ 979	$ 748	$ 918
Restricted cash and securities	7	8
Receivables, less allowances for doubtful accounts	731	714
Due from affiliates	0	0
Other	167	141
Total Current Assets	1,515	1,842
Property, Plant and Equipment, net	8,144	8,199
Restricted Cash and Securities	33	35
Goodwill and Other Intangibles Assets, net	2,806	2,833
Investment in Subsidiaries	0	0
Other Assets, net	384	398
Total Assets	12,882	13,307
Liabilities and Stockholders' Equity:
Accounts payable	730	779
Current portion of long-term debt	38	216
Accrued payroll and employee benefits	129	211
Accrued interest	179	209
Current portion of deferred revenue	236	251
Due to affiliates	0	0
Other	176	136
Total Current Liabilities	1,488	1,802
Long-Term Debt, less current portion	8,508	8,516
Deferred Revenue, less current portion	893	887
Other Liabilities	885	931
Commitments and Contingencies	0	0
Stockholders' Equity (Deficit)	1,108	1,171
Total Liabilities and Stockholders’ Equity (Deficit)	12,882	13,307
Level 3 Communications, Inc.
Current Assets:
Cash and cash equivalents	52	253	1	2
Restricted cash and securities	0	0
Receivables, less allowances for doubtful accounts	0	0
Due from affiliates	14,737	14,446
Other	4	3
Total Current Assets	14,793	14,702
Property, Plant and Equipment, net	0	0
Restricted Cash and Securities	12	12
Goodwill and Other Intangibles Assets, net	0	0
Investment in Subsidiaries	(12,072)	(11,756)
Other Assets, net	15	16
Total Assets	2,748	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	53	45
Current portion of deferred revenue	0	0
Due to affiliates	0	0
Other	1	1
Total Current Liabilities	55	219
Long-Term Debt, less current portion	1,571	1,570
Deferred Revenue, less current portion	0	0
Other Liabilities	14	14
Commitments and Contingencies	0
Stockholders' Equity (Deficit)	1,108	1,171
Total Liabilities and Stockholders’ Equity (Deficit)	2,748	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	15,986	15,709
Other	16	16
Total Current Assets	16,007	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	(21,105)	(20,470)
Other Assets, net	114	119
Total Assets	(4,984)	(4,621)
Liabilities and Stockholders' Equity:
Accounts payable	2	2
Current portion of long-term debt	6	6
Accrued payroll and employee benefits	0	0
Accrued interest	125	163
Current portion of deferred revenue	0	0
Due to affiliates	0	0
Other	47	1
Total Current Liabilities	180	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)	(12,076)	(11,760)
Total Liabilities and Stockholders’ Equity (Deficit)	(4,984)	(4,621)
Level 3 Communications, LLC
Current Assets:
Cash and cash equivalents	328	386	421	618
Restricted cash and securities	1	1
Receivables, less allowances for doubtful accounts	100	93
Due from affiliates	0	0
Other	69	49
Total Current Assets	498	529
Property, Plant and Equipment, net	2,943	2,926
Restricted Cash and Securities	17	17
Goodwill and Other Intangibles Assets, net	420	429
Investment in Subsidiaries	4,200	3,242
Other Assets, net	11	11
Total Assets	8,089	7,154
Liabilities and Stockholders' Equity:
Accounts payable	30	53
Current portion of long-term debt	2	6
Accrued payroll and employee benefits	79	161
Accrued interest	0	0
Current portion of deferred revenue	107	109
Due to affiliates	30,337	30,162
Other	44	29
Total Current Liabilities	30,599	30,520
Long-Term Debt, less current portion	19	20
Deferred Revenue, less current portion	604	602
Other Liabilities	24	75
Commitments and Contingencies	0
Stockholders' Equity (Deficit)	(23,157)	(24,063)
Total Liabilities and Stockholders’ Equity (Deficit)	8,089	7,154
Other Non-Guarantor Subsidiaries
Current Assets:
Cash and cash equivalents	225	335	320	292
Restricted cash and securities	6	7
Receivables, less allowances for doubtful accounts	631	621
Due from affiliates	0	7
Other	78	73
Total Current Assets	940	1,043
Property, Plant and Equipment, net	5,201	5,273
Restricted Cash and Securities	4	6
Goodwill and Other Intangibles Assets, net	2,386	2,404
Investment in Subsidiaries	0	0
Other Assets, net	244	252
Total Assets	8,775	8,978
Liabilities and Stockholders' Equity:
Accounts payable	697	723
Current portion of long-term debt	30	32
Accrued payroll and employee benefits	50	50
Accrued interest	1	1
Current portion of deferred revenue	129	142
Due to affiliates	386	0
Other	84	105
Total Current Liabilities	1,377	1,053
Long-Term Debt, less current portion	32	40
Deferred Revenue, less current portion	289	285
Other Liabilities	821	761
Commitments and Contingencies	0
Stockholders' Equity (Deficit)	6,256	6,839
Total Liabilities and Stockholders’ Equity (Deficit)	8,775	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	(30,723)	(30,162)
Other	0	0
Total Current Assets	(30,723)	(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	28,977	28,984
Other Assets, net	0	0
Total Assets	(1,746)	(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	(30,723)	(30,162)
Other	0	0
Total Current Liabilities	(30,723)	(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)	28,977	28,984
Total Liabilities and Stockholders’ Equity (Deficit)	$ (1,746)	$ (1,178)