Condensed Consolidating Financial Information - Statements of Operations (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Condensed Consolidating Financial Information
Revenue	$ 1,602	$ 1,569	$ 1,565	$ 1,577	$ 1,614	$ 1,590	$ 1,586	$ 1,586	$ 6,313	$ 6,376	$ 4,333
Costs and Expenses:
Cost of Revenue									2,471	2,602	1,706
Depreciation and Amortization									800	749	805
Selling, General and Administrative									2,376	2,450	1,770
Restructuring Charges					20
Total Costs and Expenses									5,647	5,801	4,281
Operating Income (Loss)	219	152	140	155	188	138	133	116	666	575	52
Other Income (Expense):
Interest Income									0	2	1
Interest expense									(649)	(733)	(716)
Interest income (expense) affiliates, net									0	0	0
Equity in net earnings (losses) of subsidiaries									0	0	0
Other income (expense), net									(88)	(218)	(123)
Total Other Expense									(737)	(949)	(838)
Loss Before Income Taxes									(71)	(374)	(786)
Income Tax Expense									(38)	(48)	(41)
Loss from Continuing Operations									(109)	(422)	(827)
Income (Loss) from Discontinued Operations, Net									0	0	71
Net Loss	14	(21)	(24)	(78)	(56)	(166)	(62)	(138)	(109)	(422)	(756)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent									10	106	18
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									(99)	(316)	(738)
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									3	2	2
Total Costs and Expenses									3	2	2
Operating Income (Loss)									(3)	(2)	(2)
Other Income (Expense):
Interest Income									0	0	0
Interest expense									(151)	(168)	(211)
Interest income (expense) affiliates, net									1,091	976	865
Equity in net earnings (losses) of subsidiaries									(1,039)	(1,188)	(1,346)
Other income (expense), net									0	(39)	(62)
Total Other Expense									(99)	(419)	(754)
Loss Before Income Taxes									(102)	(421)	(756)
Income Tax Expense									(7)	(1)	0
Loss from Continuing Operations											(756)
Income (Loss) from Discontinued Operations, Net											0
Net Loss									(109)	(422)	(756)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent									10	106	18
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									(99)	(316)	(738)
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	1	19
Total Costs and Expenses									1	1	19
Operating Income (Loss)									(1)	(1)	(19)
Other Income (Expense):
Interest Income									0	0	0
Interest expense									(497)	(535)	(471)
Interest income (expense) affiliates, net									1,706	1,598	1,423
Equity in net earnings (losses) of subsidiaries									(2,164)	(2,066)	(2,241)
Other income (expense), net									(85)	(184)	(38)
Total Other Expense									(1,040)	(1,187)	(1,327)
Loss Before Income Taxes									(1,041)	(1,188)	(1,346)
Income Tax Expense									2	0	0
Loss from Continuing Operations											(1,346)
Income (Loss) from Discontinued Operations, Net											0
Net Loss									(1,039)	(1,188)	(1,346)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent									10	106	18
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									(1,029)	(1,082)	(1,328)
Level 3 Communications, LLC
Condensed Consolidating Financial Information
Revenue									2,825	2,657	2,367
Costs and Expenses:
Cost of Revenue									1,068	996	888
Depreciation and Amortization									289	260	376
Selling, General and Administrative									1,544	1,559	1,270
Total Costs and Expenses									2,901	2,815	2,534
Operating Income (Loss)									(76)	(158)	(167)
Other Income (Expense):
Interest Income									0	1	0
Interest expense									(3)	(3)	(3)
Interest income (expense) affiliates, net									(2,679)	(2,233)	(2,065)
Equity in net earnings (losses) of subsidiaries									550	92	122
Other income (expense), net									4	6	9
Total Other Expense									(2,128)	(2,137)	(1,937)
Loss Before Income Taxes									(2,204)	(2,295)	(2,104)
Income Tax Expense									0	(4)	(15)
Loss from Continuing Operations											(2,119)
Income (Loss) from Discontinued Operations, Net											0
Net Loss									(2,204)	(2,299)	(2,119)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent									0	0	0
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									(2,204)	(2,299)	(2,119)
Other Non-Guarantor Subsidiaries
Condensed Consolidating Financial Information
Revenue									3,734	3,975	2,196
Costs and Expenses:
Cost of Revenue									1,649	1,854	1,036
Depreciation and Amortization									511	489	429
Selling, General and Administrative									828	896	491
Total Costs and Expenses									2,988	3,239	1,956
Operating Income (Loss)									746	736	240
Other Income (Expense):
Interest Income									0	1	1
Interest expense									2	(27)	(31)
Interest income (expense) affiliates, net									(118)	(341)	(223)
Equity in net earnings (losses) of subsidiaries									0	0	0
Other income (expense), net									(7)	(1)	(32)
Total Other Expense									(123)	(368)	(285)
Loss Before Income Taxes									623	368	(45)
Income Tax Expense									(33)	(43)	(26)
Loss from Continuing Operations											(71)
Income (Loss) from Discontinued Operations, Net											71
Net Loss									590	325	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent									10	16	0
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									600	341	0
Eliminations
Condensed Consolidating Financial Information
Revenue									(246)	(256)	(230)
Costs and Expenses:
Cost of Revenue									(246)	(248)	(218)
Depreciation and Amortization									0	0	0
Selling, General and Administrative									0	(8)	(12)
Total Costs and Expenses									(246)	(256)	(230)
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									2,653	3,162	3,465
Other income (expense), net									0	0	0
Total Other Expense									2,653	3,162	3,465
Loss Before Income Taxes									2,653	3,162	3,465
Income Tax Expense									0	0	0
Loss from Continuing Operations											3,465
Income (Loss) from Discontinued Operations, Net											0
Net Loss									2,653	3,162	3,465
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent									(20)	(122)	(18)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									$ 2,633	$ 3,040	$ 3,447