BUSINESS COMBINATION - Narrative (Details) $ / shares in Units, shares in Thousands, employee in Thousands, $ in Millions		6 Months Ended	12 Months Ended
	Jun. 29, 2019 USD ($) employee $ / shares shares	Jan. 03, 2020 USD ($)	Jan. 01, 2021 USD ($) employee	Dec. 31, 2018 USD ($)
Business Acquisition [Line Items]
Number of employees | employee			48
L3Harris
Business Acquisition [Line Items]
Exchange ratio	1.30
Shares issued for total merger consideration (in shares) | shares	104,100
Price per share of common stock (in dollars per share) | $ / shares	$ 189.13
Net liability off-market customer contracts	$ 139
Revenue from amortization of off-market contract liability		$ 13	$ 58
Future estimated revenue from amortization of net off-market contract liabilities in 2021			20
Future estimated revenue from amortization of net off-market contract liabilities in 2022			15
Future estimated revenue from amortization of net off-market contract liabilities in 2023			10
Future estimated revenue from amortization of net off-market contract liabilities thereafter			$ 23
L3Harris | L3
Business Acquisition [Line Items]
Number of employees | employee	31
Revenue from product sales and services — pro forma				$ 10,000
Shares issued for total merger consideration (in shares) | shares	80,080
L3Harris | Former Harris Shareholders
Business Acquisition [Line Items]
Percentage of voting interests acquired	54.00%
L3Harris | Former L3 Shareholders
Business Acquisition [Line Items]
Percentage of voting interests acquired	46.00%