Condensed Consolidating Financial Information - Statements of Cash Flows (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Consolidating Financial Information
Net Cash Provided by (Used in) Operating Activities	$ 1,161	$ 713	$ 578
Cash Flows from Investing Activities:
Capital expenditures	(910)	(760)	(743)
Increase (Decrease) in Restricted Cash and Investments	(10)	13	20
Proceeds from sale of property, plant and equipment and other assets	3	0	0
Payments to Acquire Businesses, Net of Cash Acquired	(167)	0	0
Other	(2)	2	(2)
Net Cash Used in Investing Activities	(1,086)	(745)	(725)
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs	589	1,502	4,504
Payments on and repurchases of long-term debt, including current portions and refinancing costs	(671)	(1,796)	(4,302)
Proceeds from Stock Options Exercised	0	0	5
Increase (decrease) due from affiliates, net	0	0	0
Net Cash Provided by (Used in) Financing Activities	(82)	(294)	207
Effect of Exchange Rates on Cash and Cash Equivalents	(44)	(22)	1
Net Change in Cash and Cash Equivalents	(51)	(348)	61
Cash and Cash Equivalents at Beginning of Year	631	979	918
Cash and Cash Equivalents at End of Year	580	631	979
Level 3 Communications, Inc.
Condensed Consolidating Financial Information
Net Cash Provided by (Used in) Operating Activities	(178)	(169)	(165)
Cash Flows from Investing Activities:
Capital expenditures	0	0	0
Increase (Decrease) in Restricted Cash and Investments	0	9	6
Proceeds from sale of property, plant and equipment and other assets	0
Payments to Acquire Businesses, Net of Cash Acquired	(474)
Other	0	0	0
Net Cash Used in Investing Activities	(474)	9	6
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs	590	0	293
Payments on and repurchases of long-term debt, including current portions and refinancing costs	(647)	(173)	0
Proceeds from Stock Options Exercised			5
Increase (decrease) due from affiliates, net	708	88	112
Net Cash Provided by (Used in) Financing Activities	651	(85)	410
Effect of Exchange Rates on Cash and Cash Equivalents	0	0	0
Net Change in Cash and Cash Equivalents	(1)	(245)	251
Cash and Cash Equivalents at Beginning of Year	8	253
Cash and Cash Equivalents at End of Year	7	8	253
Level 3 Financing, Inc.
Condensed Consolidating Financial Information
Net Cash Provided by (Used in) Operating Activities	(458)	(557)	(520)
Cash Flows from Investing Activities:
Capital expenditures	0	0	0
Increase (Decrease) in Restricted Cash and Investments	0	0	0
Proceeds from sale of property, plant and equipment and other assets	0
Payments to Acquire Businesses, Net of Cash Acquired	0
Other	0	0	0
Net Cash Used in Investing Activities	0	0	0
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs	0	1,502	4,211
Payments on and repurchases of long-term debt, including current portions and refinancing costs	0	(1,586)	(4,161)
Proceeds from Stock Options Exercised			0
Increase (decrease) due from affiliates, net	457	642	469
Net Cash Provided by (Used in) Financing Activities	457	558	519
Effect of Exchange Rates on Cash and Cash Equivalents	0	0	0
Net Change in Cash and Cash Equivalents	(1)	1	(1)
Cash and Cash Equivalents at Beginning of Year	6	5
Cash and Cash Equivalents at End of Year	5	6	5
Level 3 Communications, LLC
Condensed Consolidating Financial Information
Net Cash Provided by (Used in) Operating Activities	625	710	140
Cash Flows from Investing Activities:
Capital expenditures	(362)	(312)	(276)
Increase (Decrease) in Restricted Cash and Investments	2	(1)	2
Proceeds from sale of property, plant and equipment and other assets	0
Payments to Acquire Businesses, Net of Cash Acquired	0
Other	0	1	0
Net Cash Used in Investing Activities	(360)	(312)	(274)
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs	0	0	0
Payments on and repurchases of long-term debt, including current portions and refinancing costs	0	(4)	0
Proceeds from Stock Options Exercised			0
Increase (decrease) due from affiliates, net	(305)	(433)	(98)
Net Cash Provided by (Used in) Financing Activities	(305)	(437)	(98)
Effect of Exchange Rates on Cash and Cash Equivalents	0	0	0
Net Change in Cash and Cash Equivalents	(40)	(39)	(232)
Cash and Cash Equivalents at Beginning of Year	347	386
Cash and Cash Equivalents at End of Year	307	347	386
Other Non-Guarantor Subsidiaries
Condensed Consolidating Financial Information
Net Cash Provided by (Used in) Operating Activities	1,172	729	1,123
Cash Flows from Investing Activities:
Capital expenditures	(548)	(448)	(467)
Increase (Decrease) in Restricted Cash and Investments	(12)	5	12
Proceeds from sale of property, plant and equipment and other assets	3
Payments to Acquire Businesses, Net of Cash Acquired	307
Other	(2)	1	(2)
Net Cash Used in Investing Activities	(252)	(442)	(457)
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs	(1)	0	0
Payments on and repurchases of long-term debt, including current portions and refinancing costs	(24)	(33)	(141)
Proceeds from Stock Options Exercised			0
Increase (decrease) due from affiliates, net	(860)	(297)	(483)
Net Cash Provided by (Used in) Financing Activities	(885)	(330)	(624)
Effect of Exchange Rates on Cash and Cash Equivalents	(44)	(22)	1
Net Change in Cash and Cash Equivalents	(9)	(65)	43
Cash and Cash Equivalents at Beginning of Year	270	335
Cash and Cash Equivalents at End of Year	261	270	335
Eliminations
Condensed Consolidating Financial Information
Net Cash Provided by (Used in) Operating Activities	0	0	0
Cash Flows from Investing Activities:
Capital expenditures	0	0	0
Increase (Decrease) in Restricted Cash and Investments	0	0	0
Proceeds from sale of property, plant and equipment and other assets	0
Payments to Acquire Businesses, Net of Cash Acquired	0
Other	0	0	0
Net Cash Used in Investing Activities	0	0	0
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs	0	0	0
Payments on and repurchases of long-term debt, including current portions and refinancing costs	0	0	0
Proceeds from Stock Options Exercised			0
Increase (decrease) due from affiliates, net	0	0	0
Net Cash Provided by (Used in) Financing Activities	0	0	0
Effect of Exchange Rates on Cash and Cash Equivalents	0	0	0
Net Change in Cash and Cash Equivalents	0	0	0
Cash and Cash Equivalents at Beginning of Year	0	0
Cash and Cash Equivalents at End of Year	$ 0	$ 0	$ 0

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Amount of increase (decrease) in cash and cash equivalents. Cash and cash equivalents are the amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Includes effect from exchange rate changes.

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Amount of increase (decrease) from the effect of exchange rate changes on cash and cash equivalent balances held in foreign currencies.

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The net cash inflow or outflow during the period for the aggregate increase (decrease) associated with funds and investments that are not available for withdrawal or use (such as assets held in escrow or contractually limited as to use or disposition) and are associated with underlying transactions that are classified as investing activities.

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Amount of cash inflow (outflow) of investing activities, excluding discontinued operations. Investing activity cash flows include making and collecting loans and acquiring and disposing of debt or equity instruments and property, plant, and equipment and other productive assets.

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Amount of cash inflow (outflow) from operating activities, excluding discontinued operations. Operating activity cash flows include transactions, adjustments, and changes in value not defined as investing or financing activities.

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The cash outflow associated with the acquisition of a business, net of the cash acquired from the purchase.

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The cash outflow for purchases of and capital improvements on property, plant and equipment (capital expenditures), software, and other intangible assets.

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The cash inflow associated with security instrument that either represents a creditor or an ownership relationship with the holder of the investment security with a maturity of beyond one year or normal operating cycle, if longer. Includes proceeds from (a) debt, (b) capital lease obligations, (c) mandatory redeemable capital securities, and (d) any combination of (a), (b), or (c).

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The cash inflow associated with the amount received from holders exercising their stock options. This item inherently excludes any excess tax benefit, which the entity may have realized and reported separately.

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