Condensed Combining Financial Information of L-3 Communications and Its Subsidiaries - Condensed Combining Statements of Cash Flows (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 25, 2015	Sep. 26, 2014
Operating activities:
Net cash from operating activities	$ 631	$ 605
Investing activities:
Business acquisitions, net of cash acquired	(260)	$ (57)
Proceeds from sale of businesses, net of closing date cash balances	$ 308
Investments in L-3 Communications
Other investing activities	$ (134)	$ (105)
Net cash used in investing activities	(86)	(162)
Financing activities:
Proceeds from sale of Senior Notes		996
Retirement of CODES		(935)
Common stock repurchased	(605)	(413)
Dividends paid on L-3 Holdings' common stock	$ (163)	$ (158)
Dividends paid to L-3 Holdings
Investments from L-3 Holdings
Other financing activities	$ 57	$ 84
Net cash used in financing activities	(711)	(426)
Effect of foreign currency exchange rate changes on cash	(14)	(9)
Change in cash balance in assets held for sale	61
Net (decrease) increase in cash	(119)	8
Cash and cash equivalents, beginning of the period	442	500
Cash and cash equivalents, end of the period	323	508
L-3 Communications Holdings, Inc. [Member]
Operating activities:
Net cash from operating activities	768	$ 1,506
Investing activities:
Business acquisitions, net of cash acquired
Investments in L-3 Communications	(33)	$ (87)
Net cash used in investing activities	(33)	(87)
Financing activities:
Retirement of CODES		(935)
Common stock repurchased	(605)	(413)
Dividends paid on L-3 Holdings' common stock	(163)	(158)
Other financing activities	33	87
Net cash used in financing activities	(735)	$ (1,419)
Effect of foreign currency exchange rate changes on cash
Net (decrease) increase in cash
Cash and cash equivalents, beginning of the period
Cash and cash equivalents, end of the period
L-3 Communications Corporation [Member]
Operating activities:
Net cash from operating activities	337	$ 201
Investing activities:
Business acquisitions, net of cash acquired	(260)	$ (57)
Proceeds from sale of businesses, net of closing date cash balances	$ 4
Investments in L-3 Communications
Other investing activities	$ (63)	$ (37)
Net cash used in investing activities	$ (319)	(94)
Financing activities:
Proceeds from sale of Senior Notes		$ 996
Retirement of CODES
Common stock repurchased
Dividends paid on L-3 Holdings' common stock
Dividends paid to L-3 Holdings	$ (768)	$ (1,506)
Investments from L-3 Holdings	33	87
Other financing activities	526	388
Net cash used in financing activities	$ (209)	$ (35)
Effect of foreign currency exchange rate changes on cash
Change in cash balance in assets held for sale
Net (decrease) increase in cash	$ (191)	$ 72
Cash and cash equivalents, beginning of the period	361	258
Cash and cash equivalents, end of the period	170	330
Guarantor Subsidiaries [Member]
Operating activities:
Net cash from operating activities	$ 348	$ 382
Investing activities:
Business acquisitions, net of cash acquired
Proceeds from sale of businesses, net of closing date cash balances	$ 27
Investments in L-3 Communications
Other investing activities	$ (45)	$ (52)
Net cash used in investing activities	$ (18)	$ (52)
Financing activities:
Proceeds from sale of Senior Notes
Retirement of CODES
Common stock repurchased
Dividends paid on L-3 Holdings' common stock
Dividends paid to L-3 Holdings
Investments from L-3 Holdings
Other financing activities	$ (331)	$ (329)
Net cash used in financing activities	$ (331)	$ (329)
Effect of foreign currency exchange rate changes on cash
Change in cash balance in assets held for sale	$ 1
Net (decrease) increase in cash		$ 1
Cash and cash equivalents, beginning of the period	$ 1
Cash and cash equivalents, end of the period	1	$ 1
Non-Guarantor Subsidiaries [Member]
Operating activities:
Net cash from operating activities	$ 66	$ 69
Investing activities:
Business acquisitions, net of cash acquired
Proceeds from sale of businesses, net of closing date cash balances	$ 277
Investments in L-3 Communications
Other investing activities	$ (26)	$ (16)
Net cash used in investing activities	$ 251	$ (16)
Financing activities:
Proceeds from sale of Senior Notes
Retirement of CODES
Common stock repurchased
Dividends paid on L-3 Holdings' common stock
Dividends paid to L-3 Holdings
Investments from L-3 Holdings
Other financing activities	$ (338)	$ (66)
Net cash used in financing activities	(338)	(66)
Effect of foreign currency exchange rate changes on cash	(14)	(9)
Change in cash balance in assets held for sale	60
Net (decrease) increase in cash	25	(22)
Cash and cash equivalents, beginning of the period	142	261
Cash and cash equivalents, end of the period	167	239
Eliminations [Member]
Operating activities:
Net cash from operating activities	$ (888)	$ (1,553)
Investing activities:
Business acquisitions, net of cash acquired
Proceeds from sale of businesses, net of closing date cash balances
Investments in L-3 Communications	$ 33	$ 87
Other investing activities
Net cash used in investing activities	$ 33	$ 87
Financing activities:
Proceeds from sale of Senior Notes
Retirement of CODES
Common stock repurchased
Dividends paid on L-3 Holdings' common stock
Dividends paid to L-3 Holdings	$ 768	$ 1,506
Investments from L-3 Holdings	(33)	(87)
Other financing activities	167	4
Net cash used in financing activities	$ 902	$ 1,423
Effect of foreign currency exchange rate changes on cash
Change in cash balance in assets held for sale
Net (decrease) increase in cash	$ 47	$ (43)
Cash and cash equivalents, beginning of the period	(62)	(19)
Cash and cash equivalents, end of the period	$ (15)	$ (62)