Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net Income	$ 46,635	$ 41,999	$ 89,600	$ 63,085
Foreign currency translation adjustments:
Translation adjustments arising during the period	(31,167)	9,638	(19,603)	23,306
Unrealized gains on available-for-sale securities:
Unrealized gains for the period, net	0	13,976	0	23,534
Pension and other postretirement plans:
Amortization of net prior service cost included in net income	70	120	146	240
Amortization of net actuarial gain included in net income	(3,294)	(1,568)	(4,661)	(3,391)
Total pension and other postretirement plans, before tax	(3,224)	(1,448)	(4,515)	(3,151)
Cash flow hedge gain (loss)	371	(19)	607	(143)
Other Comprehensive (Loss) Income, Before Tax	(34,020)	22,147	(23,511)	43,546
Income tax benefit (expense) related to items of other comprehensive (loss) income	799	(5,008)	1,102	(8,125)
Other Comprehensive (Loss) Income, Net of Tax	(33,221)	17,139	(22,409)	35,421
Comprehensive Income	13,414	59,138	67,191	98,506
Comprehensive income attributable to noncontrolling interests	(69)	(3)	(143)	(3)
Total Comprehensive Income Attributable to Graham Holdings Company	$ 13,345	$ 59,135	$ 67,048	$ 98,503