Comprehensive Income and Accumulated Other Comprehensive Income (Loss) - Total Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 27, 2020	Jun. 28, 2020	Mar. 29, 2020	Sep. 29, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 27, 2020	Sep. 29, 2019
Equity [Abstract]
Net loss	$ 17,081	$ (67,881)	$ (11,219)	$ (297,015)	$ 42,290	$ 25,178	$ (62,019)	$ (229,547)
Foreign currency translation adjustments, net of $0.0 million, $0.2 million, $1.0 million, and $0.6 million tax, respectively	(52,910)			33,732			(75,791)	45,619
Adjustments to pension and postretirement liability, net of $0.1 million, $0.0 million, $0.3 million, and $0.2 million tax, respectively	1,136			120			1,891	591
Total comprehensive loss	(34,693)			(263,163)			(135,919)	(183,337)
Less: Comprehensive income attributable to noncontrolling interests	228			367			219	474
Comprehensive loss attributable to Belden	(34,921)			(263,530)			(136,138)	(183,811)
Foreign currency translation, tax income (loss)	(0)			(200)			(1,000)	(600)
Adjustments to pension and postretirement liability, Tax	$ 100			$ 0			$ 300	$ 200