Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net Income	$ 299,968	$ 327,879	$ 271,408
Foreign currency translation adjustments:
Translation adjustments arising during the year	31,642	5,371	(35,584)
Adjustment for sale of a business with foreign operations	0	2,011	0
Total foreign currency translation adjustments	31,642	7,382	(35,584)
Pension and other postretirement plans:
Actuarial gain (loss)	365,164	231,104	(101,013)
Prior service (cost) credit	(69)	(5,725)	4,262
Amortization of net actuarial loss (gain) included in net income	1,219	(2,046)	(11,349)
Amortization of net prior service cost (credit) included in net income	2,680	(4,142)	(947)
Curtailments and settlements included in net income	0	(91,676)	(30,267)
Total pension and other postretirement plans	368,994	127,515	(139,314)
Cash flow hedges (loss) gain	(1,282)	(1,344)
Cash flow hedges (loss) gain			551
Other Comprehensive Income (Loss), Before Tax	399,354	133,553	(174,347)
Income tax (expense) benefit related to items of other comprehensive income (loss)	(99,335)	(34,087)	37,510
Other Comprehensive Income (Loss), Net of Tax	300,019	99,466	(136,837)
Comprehensive Income	599,987	427,345	134,571
Comprehensive loss (income) attributable to noncontrolling interests	397	(24)	(202)
Total Comprehensive Income Attributable to Graham Holdings Company	$ 600,384	$ 427,321	$ 134,369