Condensed Consolidating Financial Information - Statements of Operations (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Condensed Consolidating Financial Information
Revenue	$ 1,577	$ 1,586
Costs and Expenses:
Cost of Revenue	629	657
Depreciation and Amortization	194	187
Selling, General and Administrative	599	626
Total Costs and Expenses	1,422	1,470
Operating Income (Loss)	155	116
Other Income (Expense):
Interest income	0	1
Interest expense	(169)	(189)
Interest income (expense) affiliates, net	0	0
Equity in net earnings (losses) of subsidiaries	0	0
Other, net	(50)	(52)
Total Other Expense	(219)	(240)
Income (Loss) Before Income Taxes	(64)	(124)
Income Tax Expense	(14)	(14)
Net Income (Loss)	(78)	(138)
Other Comprehensive Income (Loss), Net of Income Taxes	(52)	42
Comprehensive Income (Loss)	(130)	(96)
Level 3 Communications, Inc.
Condensed Consolidating Financial Information
Revenue	0	0
Costs and Expenses:
Cost of Revenue	0	0
Depreciation and Amortization	0	0
Selling, General and Administrative	1	1
Total Costs and Expenses	1	1
Operating Income (Loss)	(1)	(1)
Other Income (Expense):
Interest income		0
Interest expense	(39)	(42)
Interest income (expense) affiliates, net	273	245
Equity in net earnings (losses) of subsidiaries	(311)	(301)
Other, net	0	(39)
Total Other Expense	(77)	(137)
Income (Loss) Before Income Taxes	(78)	(138)
Income Tax Expense	0	0
Net Income (Loss)	(78)	(138)
Other Comprehensive Income (Loss), Net of Income Taxes	(52)	42
Comprehensive Income (Loss)	(130)	(96)
Level 3 Financing, Inc.
Condensed Consolidating Financial Information
Revenue	0	0
Costs and Expenses:
Cost of Revenue	0	0
Depreciation and Amortization	0	0
Selling, General and Administrative	0	0
Total Costs and Expenses	0	0
Operating Income (Loss)	0	0
Other Income (Expense):
Interest income		0
Interest expense	(126)	(139)
Interest income (expense) affiliates, net	430	399
Equity in net earnings (losses) of subsidiaries	(614)	(539)
Other, net	(1)	(22)
Total Other Expense	(311)	(301)
Income (Loss) Before Income Taxes	(311)	(301)
Income Tax Expense	0	0
Net Income (Loss)	(311)	(301)
Other Comprehensive Income (Loss), Net of Income Taxes	(52)	42
Comprehensive Income (Loss)	(363)	(259)
Level 3 Communications, LLC
Condensed Consolidating Financial Information
Revenue	685	626
Costs and Expenses:
Cost of Revenue	261	236
Depreciation and Amortization	71	67
Selling, General and Administrative	381	401
Total Costs and Expenses	713	704
Operating Income (Loss)	(28)	(78)
Other Income (Expense):
Interest income		1
Interest expense	(1)	0
Interest income (expense) affiliates, net	(669)	(559)
Equity in net earnings (losses) of subsidiaries	146	36
Other, net	1	1
Total Other Expense	(523)	(521)
Income (Loss) Before Income Taxes	(551)	(599)
Income Tax Expense	(1)	(1)
Net Income (Loss)	(552)	(600)
Other Comprehensive Income (Loss), Net of Income Taxes	0	0
Comprehensive Income (Loss)	(552)	(600)
Other Non-Guarantor Subsidiaries
Condensed Consolidating Financial Information
Revenue	956	1,023
Costs and Expenses:
Cost of Revenue	432	481
Depreciation and Amortization	123	120
Selling, General and Administrative	217	227
Total Costs and Expenses	772	828
Operating Income (Loss)	184	195
Other Income (Expense):
Interest income		0
Interest expense	(3)	(8)
Interest income (expense) affiliates, net	(34)	(85)
Equity in net earnings (losses) of subsidiaries	0	0
Other, net	(50)	8
Total Other Expense	(87)	(85)
Income (Loss) Before Income Taxes	97	110
Income Tax Expense	(13)	(13)
Net Income (Loss)	84	97
Other Comprehensive Income (Loss), Net of Income Taxes	(52)	35
Comprehensive Income (Loss)	32	132
Eliminations
Condensed Consolidating Financial Information
Revenue	(64)	(63)
Costs and Expenses:
Cost of Revenue	(64)	(60)
Depreciation and Amortization	0	0
Selling, General and Administrative	0	(3)
Total Costs and Expenses	(64)	(63)
Operating Income (Loss)	0	0
Other Income (Expense):
Interest income		0
Interest expense	0	0
Interest income (expense) affiliates, net	0	0
Equity in net earnings (losses) of subsidiaries	779	804
Other, net	0	0
Total Other Expense	779	804
Income (Loss) Before Income Taxes	779	804
Income Tax Expense	0	0
Net Income (Loss)	779	804
Other Comprehensive Income (Loss), Net of Income Taxes	104	(77)
Comprehensive Income (Loss)	$ 883	$ 727