Condensed Consolidating Financial Information - Statements of Operations (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Condensed Consolidating Financial Information
Revenue	$ 2,061	$ 1,625	$ 4,114	$ 3,234
Costs and Expenses:
Network Access Costs	696	613	1,419	1,227
Network Related Expenses	363	302	719	594
Depreciation and Amortization	288	187	576	371
Selling, General and Administrative Expenses	364	267	734	522
Total Costs and Expenses	1,711	1,369	3,448	2,714
Operating Income (Loss)	350	256	666	520
Other Income (Expense):
Interest Income	0	0	1	0
Interest expense	(165)	(149)	(345)	(300)
Interest income (expense) affiliates, net	0	0	0	0
Equity in net earnings (losses) of subsidiaries	0	0	0	0
Other, net	(180)	(44)	(190)	(38)
Total Other Expense	(345)	(193)	(534)	(338)
Income (Loss) before Income Taxes	5	63	132	182
Income Tax Expense	(18)	(12)	(23)	(19)
Net Income (Loss)	(13)	51	109	163
Other Comprehensive Income (Loss), Net of Income Taxes	85	13	(56)	19
Comprehensive Income (Loss)	72	64	53	182
Level 3 Communications, Inc.
Condensed Consolidating Financial Information
Revenue	0	0	0	0
Costs and Expenses:
Network Access Costs	0	0	0	0
Network Related Expenses	0	0	0	0
Depreciation and Amortization	0	0	0	0
Selling, General and Administrative Expenses	1	1	2	1
Total Costs and Expenses	1	1	2	1
Operating Income (Loss)	(1)	(1)	(2)	(1)
Other Income (Expense):
Interest Income	0		0
Interest expense	(14)	(34)	(33)	(68)
Interest income (expense) affiliates, net	331	303	664	591
Equity in net earnings (losses) of subsidiaries	(311)	(217)	(502)	(359)
Other, net	(18)	0	(18)	0
Total Other Expense	(12)	52	111	164
Income (Loss) before Income Taxes	(13)	51	109	163
Income Tax Expense	0	0	0	0
Net Income (Loss)	(13)	51	109	163
Other Comprehensive Income (Loss), Net of Income Taxes	85	13	(56)	19
Comprehensive Income (Loss)	72	64	53	182
Level 3 Financing, Inc.
Condensed Consolidating Financial Information
Revenue	0	0	0	0
Costs and Expenses:
Network Access Costs	0	0	0	0
Network Related Expenses	0	0	0	0
Depreciation and Amortization	0	0	0	0
Selling, General and Administrative Expenses	0	1	0	1
Total Costs and Expenses	0	1	0	1
Operating Income (Loss)	0	(1)	0	(1)
Other Income (Expense):
Interest Income	0		0
Interest expense	(146)	(113)	(301)	(225)
Interest income (expense) affiliates, net	496	459	997	918
Equity in net earnings (losses) of subsidiaries	(516)	(561)	(1,052)	(1,049)
Other, net	(145)	0	(145)	0
Total Other Expense	(311)	(215)	(501)	(356)
Income (Loss) before Income Taxes	(311)	(216)	(501)	(357)
Income Tax Expense	0	(1)	(1)	(2)
Net Income (Loss)	(311)	(217)	(502)	(359)
Other Comprehensive Income (Loss), Net of Income Taxes	0	0	0	0
Comprehensive Income (Loss)	(311)	(217)	(502)	(359)
Level 3 Communications, LLC
Condensed Consolidating Financial Information
Revenue	830	760	1,648	1,497
Costs and Expenses:
Network Access Costs	299	288	619	578
Network Related Expenses	231	190	461	372
Depreciation and Amortization	75	69	149	139
Selling, General and Administrative Expenses	268	181	515	324
Total Costs and Expenses	873	728	1,744	1,413
Operating Income (Loss)	(43)	32	(96)	84
Other Income (Expense):
Interest Income	0		0
Interest expense	(1)	1	(2)	0
Interest income (expense) affiliates, net	(769)	(727)	(1,535)	(1,439)
Equity in net earnings (losses) of subsidiaries	0	162	177	340
Other, net	(3)	1	(1)	4
Total Other Expense	(773)	(563)	(1,361)	(1,095)
Income (Loss) before Income Taxes	(816)	(531)	(1,457)	(1,011)
Income Tax Expense	0	0	0	(1)
Net Income (Loss)	(816)	(531)	(1,457)	(1,012)
Other Comprehensive Income (Loss), Net of Income Taxes	0	0	0	0
Comprehensive Income (Loss)	(816)	(531)	(1,457)	(1,012)
Other Non-Guarantor Subsidiaries
Condensed Consolidating Financial Information
Revenue	1,276	918	2,563	1,849
Costs and Expenses:
Network Access Costs	442	378	897	761
Network Related Expenses	132	112	258	222
Depreciation and Amortization	213	118	427	232
Selling, General and Administrative Expenses	95	84	217	196
Total Costs and Expenses	882	692	1,799	1,411
Operating Income (Loss)	394	226	764	438
Other Income (Expense):
Interest Income	0		1
Interest expense	(4)	(3)	(9)	(7)
Interest income (expense) affiliates, net	(58)	(35)	(126)	(70)
Equity in net earnings (losses) of subsidiaries	0	0	0	0
Other, net	(14)	(45)	(26)	(42)
Total Other Expense	(76)	(83)	(160)	(119)
Income (Loss) before Income Taxes	318	143	604	319
Income Tax Expense	(18)	(11)	(22)	(16)
Net Income (Loss)	300	132	582	303
Other Comprehensive Income (Loss), Net of Income Taxes	197	13	56	19
Comprehensive Income (Loss)	497	145	638	322
Eliminations
Condensed Consolidating Financial Information
Revenue	(45)	(53)	(97)	(112)
Costs and Expenses:
Network Access Costs	(45)	(53)	(97)	(112)
Network Related Expenses	0	0	0	0
Depreciation and Amortization	0	0	0	0
Selling, General and Administrative Expenses	0	0	0	0
Total Costs and Expenses	(45)	(53)	(97)	(112)
Operating Income (Loss)	0	0	0	0
Other Income (Expense):
Interest Income	0		0
Interest expense	0	0	0	0
Interest income (expense) affiliates, net	0	0	0	0
Equity in net earnings (losses) of subsidiaries	827	616	1,377	1,068
Other, net	0	0	0	0
Total Other Expense	827	616	1,377	1,068
Income (Loss) before Income Taxes	827	616	1,377	1,068
Income Tax Expense	0	0	0	0
Net Income (Loss)	827	616	1,377	1,068
Other Comprehensive Income (Loss), Net of Income Taxes	(197)	(13)	(56)	(19)
Comprehensive Income (Loss)	$ 630	$ 603	$ 1,321	$ 1,049