Condensed Consolidating Financial Information - Statements of Operations (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Condensed Consolidating Financial Information
Revenue	$ 1,614	$ 1,590	$ 1,586	$ 1,586	$ 1,579	$ 927	$ 913	$ 914	$ 6,376	$ 4,333	$ 3,591
Costs and Expenses:
Cost of Revenue									2,602	1,706	1,434
Depreciation and Amortization									749	805	870
Selling, General and Administrative									2,416	1,759	1,373
Restructuring Charges	20				11				34	11	2
Total Costs and Expenses									5,801	4,281	3,679
Operating Income (Loss)	188	138	133	116	45	7	3	(3)	575	52	(88)
Other Income (Expense):
Interest Income									2	1	1
Interest expense									(733)	(716)	(586)
Interest income (expense) affiliates, net									0	0	0
Equity in net earnings (losses) of subsidiaries									0	0	0
Other income (expense), net									(218)	(123)	(39)
Total Other Expense									(949)	(838)	(624)
Loss Before Income Taxes									(374)	(786)	(712)
Income Tax Expense									(48)	(41)	91
Loss from Continuing Operations									(422)	(827)	(621)
Income (Loss) from Discontinued Operations, Net									0	71	(1)
Net Loss	(56)	(166)	(62)	(138)	(163)	(207)	(181)	(205)	(422)	(756)	(622)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent									106	18	(93)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									(316)	(738)	(715)
Level 3 Communications, Inc.
Condensed Consolidating Financial Information
Revenue									0	0	0
Costs and Expenses:
Cost of Revenue									0	0	0
Depreciation and Amortization									0	0	0
Selling, General and Administrative									2	2	2
Restructuring Charges									0	0	0
Total Costs and Expenses									2	2	2
Operating Income (Loss)									(2)	(2)	(2)
Other Income (Expense):
Interest Income									0	0	0
Interest expense									(168)	(211)	(199)
Interest income (expense) affiliates, net									976	865	795
Equity in net earnings (losses) of subsidiaries									(1,188)	(1,346)	(1,221)
Other income (expense), net									(39)	(62)	5
Total Other Expense									(419)	(754)	(620)
Loss Before Income Taxes									(421)	(756)	(622)
Income Tax Expense									(1)	0	0
Loss from Continuing Operations										(756)	(622)
Income (Loss) from Discontinued Operations, Net										0	0
Net Loss									(422)	(756)	(622)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent									106	18	(93)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									(316)	(738)	(715)
Level 3 Financing, Inc.
Condensed Consolidating Financial Information
Revenue									0	0	0
Costs and Expenses:
Cost of Revenue									0	0	0
Depreciation and Amortization									0	0	0
Selling, General and Administrative									1	19	0
Restructuring Charges									0	0	0
Total Costs and Expenses									1	19	0
Operating Income (Loss)									(1)	(19)	0
Other Income (Expense):
Interest Income									0	0	0
Interest expense									(535)	(471)	(377)
Interest income (expense) affiliates, net									1,598	1,423	1,298
Equity in net earnings (losses) of subsidiaries									(2,066)	(2,241)	(2,087)
Other income (expense), net									(184)	(38)	(55)
Total Other Expense									(1,187)	(1,327)	(1,221)
Loss Before Income Taxes									(1,188)	(1,346)	(1,221)
Income Tax Expense									0	0	0
Loss from Continuing Operations										(1,346)	(1,221)
Income (Loss) from Discontinued Operations, Net										0	0
Net Loss									(1,188)	(1,346)	(1,221)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent									106	18	(93)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									(1,082)	(1,328)	(1,314)
Level 3 Communications, LLC
Condensed Consolidating Financial Information
Revenue									2,657	2,367	2,046
Costs and Expenses:
Cost of Revenue									996	888	800
Depreciation and Amortization									260	376	429
Selling, General and Administrative									1,541	1,269	1,185
Restructuring Charges									18	1	1
Total Costs and Expenses									2,815	2,534	2,415
Operating Income (Loss)									(158)	(167)	(369)
Other Income (Expense):
Interest Income									1	0	1
Interest expense									(3)	(3)	(2)
Interest income (expense) affiliates, net									(2,233)	(2,065)	(1,891)
Equity in net earnings (losses) of subsidiaries									92	122	218
Other income (expense), net									6	9	1
Total Other Expense									(2,137)	(1,937)	(1,673)
Loss Before Income Taxes									(2,295)	(2,104)	(2,042)
Income Tax Expense									(4)	(15)	(1)
Loss from Continuing Operations										(2,119)	(2,043)
Income (Loss) from Discontinued Operations, Net										0	0
Net Loss									(2,299)	(2,119)	(2,043)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent									0	0	0
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									(2,299)	(2,119)	(2,043)
Other Non-Guarantor Subsidiaries
Condensed Consolidating Financial Information
Revenue									3,975	2,196	1,774
Costs and Expenses:
Cost of Revenue									1,854	1,036	851
Depreciation and Amortization									489	429	441
Selling, General and Administrative									880	481	198
Restructuring Charges									16	10	1
Total Costs and Expenses									3,239	1,956	1,491
Operating Income (Loss)									736	240	283
Other Income (Expense):
Interest Income									1	1	0
Interest expense									(27)	(31)	(8)
Interest income (expense) affiliates, net									(341)	(223)	(202)
Equity in net earnings (losses) of subsidiaries									0	0	0
Other income (expense), net									(1)	(32)	10
Total Other Expense									(368)	(285)	(200)
Loss Before Income Taxes									368	(45)	83
Income Tax Expense									(43)	(26)	92
Loss from Continuing Operations										(71)	175
Income (Loss) from Discontinued Operations, Net										71	(1)
Net Loss									325	0	174
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent									16	0	(77)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									341	0	97
Eliminations
Condensed Consolidating Financial Information
Revenue									(256)	(230)	(229)
Costs and Expenses:
Cost of Revenue									(248)	(218)	(217)
Depreciation and Amortization									0	0	0
Selling, General and Administrative									(8)	(12)	(12)
Restructuring Charges									0	0	0
Total Costs and Expenses									(256)	(230)	(229)
Operating Income (Loss)									0	0	0
Other Income (Expense):
Interest Income									0	0	0
Interest expense									0	0	0
Interest income (expense) affiliates, net									0	0	0
Equity in net earnings (losses) of subsidiaries									3,162	3,465	3,090
Other income (expense), net									0	0	0
Total Other Expense									3,162	3,465	3,090
Loss Before Income Taxes									3,162	3,465	3,090
Income Tax Expense									0	0	0
Loss from Continuing Operations										3,465	3,090
Income (Loss) from Discontinued Operations, Net										0	0
Net Loss									3,162	3,465	3,090
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent									(122)	(18)	170
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									$ 3,040	$ 3,447	$ 3,260