Condensed Consolidating Financial Information - Balance Sheets (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
Current Assets:
Cash and cash equivalents	$ 1,291	$ 854	$ 549	$ 580
Restricted cash and securities	8	8
Receivables, less allowances for doubtful accounts	839	757
Due from affiliates	0	0
Other	140	111
Total Current Assets	2,278	1,730
Property, Plant and Equipment, net	10,073	9,878
Restricted Cash and Securities	31	42
Goodwill and Other Intangibles Assets, net	8,759	8,876
Investment in Subsidiaries	0	0
Deferred Tax Assets	3,343	3,441
Other Assets, net	50	50
Total Assets	24,534	24,017
Liabilities and Stockholders' Equity:
Accounts payable	762	629
Current portion of long-term debt	7	15
Accrued payroll and employee benefits	160	218
Accrued interest	131	108
Current portion of deferred revenue	268	267
Due to affiliates	0	0
Other	171	179
Total Current Liabilities	1,499	1,416
Long-Term Debt, less current portion	10,871	10,866
Deferred Revenue, less current portion	1,027	977
Other Liabilities	637	632
Commitments and Contingencies
Stockholders' Equity (Deficit)	10,500	10,126
Total Liabilities and Stockholders’ Equity (Deficit)	24,534	24,017
Level 3 Communications, Inc.
Current Assets:
Cash and cash equivalents	11	12	13	7
Restricted cash and securities	0	0
Receivables, less allowances for doubtful accounts	0	0
Due from affiliates	13,140	12,415
Other	0	0
Total Current Assets	13,151	12,427
Property, Plant and Equipment, net	0	0
Restricted Cash and Securities	22	27
Goodwill and Other Intangibles Assets, net	0	0
Investment in Subsidiaries	16,816	16,772
Deferred Tax Assets	44	38
Other Assets, net	0	0
Total Assets	30,033	29,264
Liabilities and Stockholders' Equity:
Accounts payable	0	0
Current portion of long-term debt	0	0
Accrued payroll and employee benefits	0	0
Accrued interest	11	11
Current portion of deferred revenue	0	0
Due to affiliates	0	0
Other	0	0
Total Current Liabilities	11	11
Long-Term Debt, less current portion	592	591
Deferred Revenue, less current portion	0	0
Other Liabilities	15	15
Commitments and Contingencies
Stockholders' Equity (Deficit)	29,415	28,647
Total Liabilities and Stockholders’ Equity (Deficit)	30,033	29,264
Level 3 Financing, Inc.
Current Assets:
Cash and cash equivalents	6	6	5	5
Restricted cash and securities	0	0
Receivables, less allowances for doubtful accounts	0	0
Due from affiliates	23,715	22,759
Other	0	0
Total Current Assets	23,721	22,765
Property, Plant and Equipment, net	0	0
Restricted Cash and Securities	0	0
Goodwill and Other Intangibles Assets, net	0	0
Investment in Subsidiaries	17,713	17,714
Deferred Tax Assets	2,717	2,847
Other Assets, net	0	0
Total Assets	44,151	43,326
Liabilities and Stockholders' Equity:
Accounts payable	0	1
Current portion of long-term debt	0	0
Accrued payroll and employee benefits	0	0
Accrued interest	112	90
Current portion of deferred revenue	0	0
Due to affiliates	0	0
Other	0	0
Total Current Liabilities	112	91
Long-Term Debt, less current portion	10,099	10,092
Deferred Revenue, less current portion	0	0
Other Liabilities	0	0
Commitments and Contingencies
Stockholders' Equity (Deficit)	33,940	33,143
Total Liabilities and Stockholders’ Equity (Deficit)	44,151	43,326
Level 3 Communications, LLC
Current Assets:
Cash and cash equivalents	1,202	727	289	307
Restricted cash and securities	1	1
Receivables, less allowances for doubtful accounts	81	47
Due from affiliates	0	0
Other	90	56
Total Current Assets	1,374	831
Property, Plant and Equipment, net	3,645	3,423
Restricted Cash and Securities	9	14
Goodwill and Other Intangibles Assets, net	358	363
Investment in Subsidiaries	3,730	3,734
Deferred Tax Assets	0	0
Other Assets, net	12	12
Total Assets	9,128	8,377
Liabilities and Stockholders' Equity:
Accounts payable	360	195
Current portion of long-term debt	2	2
Accrued payroll and employee benefits	125	186
Accrued interest	0	0
Current portion of deferred revenue	108	119
Due to affiliates	39,420	37,990
Other	124	115
Total Current Liabilities	40,139	38,607
Long-Term Debt, less current portion	14	15
Deferred Revenue, less current portion	725	680
Other Liabilities	140	133
Commitments and Contingencies
Stockholders' Equity (Deficit)	(31,890)	(31,058)
Total Liabilities and Stockholders’ Equity (Deficit)	9,128	8,377
Other Non-Guarantor Subsidiaries
Current Assets:
Cash and cash equivalents	72	109	242	261
Restricted cash and securities	7	7
Receivables, less allowances for doubtful accounts	758	710
Due from affiliates	2,565	2,816
Other	50	55
Total Current Assets	3,452	3,697
Property, Plant and Equipment, net	6,428	6,455
Restricted Cash and Securities	0	1
Goodwill and Other Intangibles Assets, net	8,401	8,513
Investment in Subsidiaries	0	0
Deferred Tax Assets	582	556
Other Assets, net	38	38
Total Assets	18,901	19,260
Liabilities and Stockholders' Equity:
Accounts payable	402	433
Current portion of long-term debt	5	13
Accrued payroll and employee benefits	35	32
Accrued interest	8	7
Current portion of deferred revenue	160	148
Due to affiliates	0	0
Other	47	64
Total Current Liabilities	657	697
Long-Term Debt, less current portion	166	168
Deferred Revenue, less current portion	302	297
Other Liabilities	482	484
Commitments and Contingencies
Stockholders' Equity (Deficit)	17,294	17,614
Total Liabilities and Stockholders’ Equity (Deficit)	18,901	19,260
Eliminations
Current Assets:
Cash and cash equivalents	0	0	$ 0	$ 0
Restricted cash and securities	0	0
Receivables, less allowances for doubtful accounts	0	0
Due from affiliates	(39,420)	(37,990)
Other	0	0
Total Current Assets	(39,420)	(37,990)
Property, Plant and Equipment, net	0	0
Restricted Cash and Securities	0	0
Goodwill and Other Intangibles Assets, net	0	0
Investment in Subsidiaries	(38,259)	(38,220)
Deferred Tax Assets	0	0
Other Assets, net	0	0
Total Assets	(77,679)	(76,210)
Liabilities and Stockholders' Equity:
Accounts payable	0	0
Current portion of long-term debt	0	0
Accrued payroll and employee benefits	0	0
Accrued interest	0	0
Current portion of deferred revenue	0	0
Due to affiliates	(39,420)	(37,990)
Other	0	0
Total Current Liabilities	(39,420)	(37,990)
Long-Term Debt, less current portion	0	0
Deferred Revenue, less current portion	0	0
Other Liabilities	0	0
Commitments and Contingencies
Stockholders' Equity (Deficit)	(38,259)	(38,220)
Total Liabilities and Stockholders’ Equity (Deficit)	$ (77,679)	$ (76,210)