Condensed Consolidating Financial Information - Statements of Operations (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Condensed Consolidating Financial Information
Revenue	$ 1,569	$ 1,590	$ 4,711	$ 4,762
Costs and Expenses:
Cost of Revenue	608	642	1,853	1,947
Depreciation and Amortization	203	185	596	563
Selling, General and Administrative	606	625	1,815	1,865
Total Costs and Expenses	1,417	1,452	4,264	4,375
Operating Income (Loss)	152	138	447	387
Other Income (Expense):
Interest income	0	0	0	2
Interest expense	(165)	(188)	(501)	(558)
Interest income (expense) affiliates, net	0	0	0	0
Equity in net earnings (losses) of subsidiaries	0	0	0	0
Other, net	6	(103)	(30)	(162)
Total Other Expense	(159)	(291)	(531)	(718)
Income (Loss) before Income Taxes	(7)	(153)	(84)	(331)
Income Tax Expense	(14)	(13)	(39)	(35)
Net Income (Loss)	(21)	(166)	(123)	(366)
Other Comprehensive Income (Loss), Net of Income Taxes	42	122	(21)	108
Comprehensive Income (Loss)	21	(44)	(144)	(258)
Level 3 Communications, Inc.
Condensed Consolidating Financial Information
Revenue	0	0	0	0
Costs and Expenses:
Cost of Revenue	0	0	0	0
Depreciation and Amortization	0	0	0	0
Selling, General and Administrative	1	1	2	2
Total Costs and Expenses	1	1	2	2
Operating Income (Loss)	(1)	(1)	(2)	(2)
Other Income (Expense):
Interest income		0		0
Interest expense	(38)	(43)	(114)	(123)
Interest income (expense) affiliates, net	274	244	819	734
Equity in net earnings (losses) of subsidiaries	(255)	(365)	(825)	(935)
Other, net	0	0	0	(39)
Total Other Expense	(19)	(164)	(120)	(363)
Income (Loss) before Income Taxes	(20)	(165)	(122)	(365)
Income Tax Expense	(1)	(1)	(1)	(1)
Net Income (Loss)	(21)	(166)	(123)	(366)
Other Comprehensive Income (Loss), Net of Income Taxes	42	122	(21)	108
Comprehensive Income (Loss)	21	(44)	(144)	(258)
Level 3 Financing, Inc.
Condensed Consolidating Financial Information
Revenue	0	0	0	0
Costs and Expenses:
Cost of Revenue	0	0	0	0
Depreciation and Amortization	0	0	0	0
Selling, General and Administrative	1	1	1	1
Total Costs and Expenses	1	1	1	1
Operating Income (Loss)	(1)	(1)	(1)	(1)
Other Income (Expense):
Interest income		0		0
Interest expense	(123)	(137)	(374)	(410)
Interest income (expense) affiliates, net	429	400	1,284	1,202
Equity in net earnings (losses) of subsidiaries	(542)	(516)	(1,715)	(1,593)
Other, net	(18)	(111)	(19)	(133)
Total Other Expense	(254)	(364)	(824)	(934)
Income (Loss) before Income Taxes	(255)	(365)	(825)	(935)
Income Tax Expense	0	0	0	0
Net Income (Loss)	(255)	(365)	(825)	(935)
Other Comprehensive Income (Loss), Net of Income Taxes	42	122	(21)	108
Comprehensive Income (Loss)	(213)	(243)	(846)	(827)
Level 3 Communications, LLC
Condensed Consolidating Financial Information
Revenue	711	672	2,090	1,957
Costs and Expenses:
Cost of Revenue	264	256	781	736
Depreciation and Amortization	73	63	215	196
Selling, General and Administrative	385	410	1,178	1,207
Total Costs and Expenses	722	729	2,174	2,139
Operating Income (Loss)	(11)	(57)	(84)	(182)
Other Income (Expense):
Interest income		0		1
Interest expense	(1)	(1)	(2)	(2)
Interest income (expense) affiliates, net	(670)	(561)	(2,008)	(1,678)
Equity in net earnings (losses) of subsidiaries	122	40	398	101
Other, net	1	3	3	6
Total Other Expense	(548)	(519)	(1,609)	(1,572)
Income (Loss) before Income Taxes	(559)	(576)	(1,693)	(1,754)
Income Tax Expense	(1)	(1)	(2)	(3)
Net Income (Loss)	(560)	(577)	(1,695)	(1,757)
Other Comprehensive Income (Loss), Net of Income Taxes	0	0	0	0
Comprehensive Income (Loss)	(560)	(577)	(1,695)	(1,757)
Other Non-Guarantor Subsidiaries
Condensed Consolidating Financial Information
Revenue	919	981	2,803	2,995
Costs and Expenses:
Cost of Revenue	405	447	1,254	1,393
Depreciation and Amortization	130	122	381	367
Selling, General and Administrative	219	215	634	663
Total Costs and Expenses	754	784	2,269	2,423
Operating Income (Loss)	165	197	534	572
Other Income (Expense):
Interest income		0		1
Interest expense	(3)	(7)	(11)	(23)
Interest income (expense) affiliates, net	(33)	(83)	(95)	(258)
Equity in net earnings (losses) of subsidiaries	0	0	0	0
Other, net	23	5	(14)	4
Total Other Expense	(13)	(85)	(120)	(276)
Income (Loss) before Income Taxes	152	112	414	296
Income Tax Expense	(12)	(11)	(36)	(31)
Net Income (Loss)	140	101	378	265
Other Comprehensive Income (Loss), Net of Income Taxes	42	48	(21)	18
Comprehensive Income (Loss)	182	149	357	283
Eliminations
Condensed Consolidating Financial Information
Revenue	(61)	(63)	(182)	(190)
Costs and Expenses:
Cost of Revenue	(61)	(61)	(182)	(182)
Depreciation and Amortization	0	0	0	0
Selling, General and Administrative	0	(2)	0	(8)
Total Costs and Expenses	(61)	(63)	(182)	(190)
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	675	841	2,142	2,427
Other, net	0	0	0	0
Total Other Expense	675	841	2,142	2,427
Income (Loss) before Income Taxes	675	841	2,142	2,427
Income Tax Expense	0	0	0	0
Net Income (Loss)	675	841	2,142	2,427
Other Comprehensive Income (Loss), Net of Income Taxes	(84)	(170)	42	(126)
Comprehensive Income (Loss)	$ 591	$ 671	$ 2,184	$ 2,301