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. 23, 2016	Sep. 25, 2015
Operating activities:
Net cash from operating activities	$ 579	$ 597
Investing activities:
Business acquisitions, net of cash acquired	(27)	(260)
Proceeds from sale of business, net of closing date cash balance	561	308
Investments in L-3 Communications
Other investing activities	(104)	(130)
Net cash from (used in) investing activities from continuing operations	430	(82)
Financing activities:
Redemption of senior notes	(298)
Common stock repurchased	(326)	(605)
Dividends paid on L-3 Holdings common stock	(166)	(163)
Dividends paid to L-3 Holdings
Investments from L-3 Holdings
Other financing activities	44	33
Net cash used in financing activities from continuing operations	(746)	(735)
Effect of foreign currency exchange rate changes on cash	(3)	(14)
Net decrease in cash and cash equivalents of discontinued operations	(56)	54
Change in cash balance in assets held for sale		61
Net (decrease) increase in cash	204	(119)
Cash and cash equivalents, beginning of the period	207	442
Cash and cash equivalents, end of the period	411	323
L-3 Communications Holdings, Inc. [Member]
Operating activities:
Net cash from operating activities	492	768
Investing activities:
Business acquisitions, net of cash acquired
Proceeds from sale of business, net of closing date cash balance
Investments in L-3 Communications	(52)	(34)
Other investing activities
Net cash from (used in) investing activities from continuing operations	(52)	(34)
Financing activities:
Redemption of senior notes
Common stock repurchased	(326)	(605)
Dividends paid on L-3 Holdings common stock	(166)	(163)
Dividends paid to L-3 Holdings
Investments from L-3 Holdings
Other financing activities	52	34
Net cash used in financing activities from continuing operations	(440)	(734)
Effect of foreign currency exchange rate changes on cash
Net decrease in cash and cash equivalents of discontinued operations
Change in cash balance in assets held for sale
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	196	370
Investing activities:
Business acquisitions, net of cash acquired	(27)	(260)
Proceeds from sale of business, net of closing date cash balance	563	4
Investments in L-3 Communications
Other investing activities	(27)	(62)
Net cash from (used in) investing activities from continuing operations	509	(318)
Financing activities:
Redemption of senior notes	(298)
Common stock repurchased
Dividends paid on L-3 Holdings common stock
Dividends paid to L-3 Holdings	(492)	(768)
Investments from L-3 Holdings	52	34
Other financing activities	84	491
Net cash used in financing activities from continuing operations	(654)	(243)
Effect of foreign currency exchange rate changes on cash
Net decrease in cash and cash equivalents of discontinued operations
Change in cash balance in assets held for sale
Net (decrease) increase in cash	51	(191)
Cash and cash equivalents, beginning of the period	137	361
Cash and cash equivalents, end of the period	188	170
Guarantor Subsidiaries [Member]
Operating activities:
Net cash from operating activities	301	282
Investing activities:
Business acquisitions, net of cash acquired
Proceeds from sale of business, net of closing date cash balance		27
Investments in L-3 Communications
Other investing activities	(47)	(42)
Net cash from (used in) investing activities from continuing operations	(47)	(15)
Financing activities:
Redemption of senior notes
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	(198)	(322)
Net cash used in financing activities from continuing operations	(198)	(322)
Effect of foreign currency exchange rate changes on cash
Net decrease in cash and cash equivalents of discontinued operations	(56)	54
Change in cash balance in assets held for sale		1
Net (decrease) increase in cash
Cash and cash equivalents, beginning of the period		1
Cash and cash equivalents, end of the period		1
Non-Guarantor Subsidiaries [Member]
Operating activities:
Net cash from operating activities	159	65
Investing activities:
Business acquisitions, net of cash acquired
Proceeds from sale of business, net of closing date cash balance	(2)	277
Investments in L-3 Communications
Other investing activities	(30)	(26)
Net cash from (used in) investing activities from continuing operations	(32)	251
Financing activities:
Redemption of senior notes
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	(50)	(337)
Net cash used in financing activities from continuing operations	(50)	(337)
Effect of foreign currency exchange rate changes on cash	(3)	(14)
Net decrease in cash and cash equivalents of discontinued operations
Change in cash balance in assets held for sale		60
Net (decrease) increase in cash	74	25
Cash and cash equivalents, beginning of the period	165	142
Cash and cash equivalents, end of the period	239	167
Eliminations [Member]
Operating activities:
Net cash from operating activities	(569)	(888)
Investing activities:
Business acquisitions, net of cash acquired
Proceeds from sale of business, net of closing date cash balance
Investments in L-3 Communications	52	34
Other investing activities
Net cash from (used in) investing activities from continuing operations	52	34
Financing activities:
Redemption of senior notes
Common stock repurchased
Dividends paid on L-3 Holdings common stock
Dividends paid to L-3 Holdings	492	768
Investments from L-3 Holdings	(52)	(34)
Other financing activities	156	167
Net cash used in financing activities from continuing operations	596	901
Effect of foreign currency exchange rate changes on cash
Net decrease in cash and cash equivalents of discontinued operations
Change in cash balance in assets held for sale
Net (decrease) increase in cash	79	47
Cash and cash equivalents, beginning of the period	(95)	(62)
Cash and cash equivalents, end of the period	$ (16)	$ (15)