Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net Income	$ 327,879	$ 271,408	$ 302,489
Foreign currency translation adjustments:
Translation adjustments arising during the year	5,371	(35,584)	33,175
Adjustment for sales of businesses with foreign operations	2,011	0	137
Total foreign currency translation adjustments	7,382	(35,584)	33,312
Unrealized gains on available-for-sale securities:
Unrealized gains for the year	0	0	112,086
Pension and other postretirement plans:
Actuarial gain (loss)	231,104	(101,013)	179,674
Prior service (cost) credit	(5,725)	4,262	(75)
Amortization of net actuarial gain included in net income	(2,046)	(11,349)	(6,527)
Amortization of net prior service (credit) cost included in net income	(4,142)	(947)	477
Curtailments and settlements included in net income	(91,676)	(30,267)	0
Total pension and other postretirement plans	127,515	(139,314)	173,549
Cash flow hedges (loss) gain	(1,344)
Cash flow hedges (loss) gain		551	112
Other Comprehensive Income (Loss), Before Tax	133,553	(174,347)	319,059
Income tax (expense) benefit related to items of other comprehensive income (loss)	(34,087)	37,510	(90,923)
Other Comprehensive Income (Loss), Net of Tax	99,466	(136,837)	228,136
Comprehensive Income	427,345	134,571	530,625
Comprehensive income attributable to noncontrolling interests	(24)	(202)	(445)
Total Comprehensive Income Attributable to Graham Holdings Company	$ 427,321	$ 134,369	$ 530,180