Comprehensive Income and Accumulated Other Comprehensive Income (Loss) - Components of Other Comprehensive Income (Loss), Net of Tax (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 965,819	$ 1,387,588
Other comprehensive gain (loss) attributable to Belden before reclassifications	(143,901)	10,376
Amounts reclassified from accumulated other comprehensive income	15,468	1,113
Net current period other comprehensive gain (loss) attributable to Belden		11,489
Ending balance	757,051	965,819
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(63,418)	(74,907)
Ending balance	(191,851)	(63,418)
Foreign Currency Translation Component
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(18,225)	(41,882)
Other comprehensive gain (loss) attributable to Belden before reclassifications	(123,101)	23,657
Amounts reclassified from accumulated other comprehensive income	10,145	0
Net current period other comprehensive gain (loss) attributable to Belden	(112,956)	23,657
Ending balance	(131,181)	(18,225)
Pension and Other Postretirement Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(45,193)	(33,025)
Other comprehensive gain (loss) attributable to Belden before reclassifications	(20,800)	(13,281)
Amounts reclassified from accumulated other comprehensive income	5,323	1,113
Net current period other comprehensive gain (loss) attributable to Belden	(15,477)	(12,168)
Ending balance	$ (60,670)	$ (45,193)