7. Accumulated Other Comprehensive Income 7. Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, Accumulated other comprehensive income			$ (87,348)
Total other comprehensive income (loss) net of tax	$ 145,113	$ (102,540)	171,319	$ (105,155)
Ending balance, Accumulated other comprehensive income	83,971		83,971
Other (income) expense, net	(1,015)	(4,367)	(21,517)	(26,959)
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, Accumulated other comprehensive income			(72,400)	(35,500)
Other Comprehensive Income (Loss), before Reclassifications, before Tax			167,400	(109,900)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax			0	0
Other Comprehensive Income (Loss), Tax			0	0
Total other comprehensive income (loss) net of tax			167,400	(109,900)
Ending balance, Accumulated other comprehensive income	95,000	(145,400)	95,000	(145,400)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, Accumulated other comprehensive income			(22,200)	(14,800)
Other Comprehensive Income (Loss), before Reclassifications, before Tax			(1,300)	100
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax			1,800	600
Other Comprehensive Income (Loss), Tax			400	(200)
Total other comprehensive income (loss) net of tax			900	500
Ending balance, Accumulated other comprehensive income	(21,300)	(14,300)	(21,300)	(14,300)
Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification Out Of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other (income) expense, net	(1,100)	(200)	(1,800)	(600)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, Accumulated other comprehensive income			7,200	3,300
Other Comprehensive Income (Loss), before Reclassifications, before Tax			4,500	5,100
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax			(600)	(300)
Other Comprehensive Income (Loss), Tax			(900)	(600)
Total other comprehensive income (loss) net of tax			3,000	4,200
Ending balance, Accumulated other comprehensive income	10,200	7,500	10,200	7,500
Accumulated Net Unrealized Investment Gain (Loss) [Member] | Reclassification Out Of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other (income) expense, net	0	(200)	(600)	(300)
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, Accumulated other comprehensive income			(87,400)	(47,000)
Other Comprehensive Income (Loss), before Reclassifications, before Tax			170,600	(104,700)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax			1,200	300
Other Comprehensive Income (Loss), Tax			(500)	(800)
Total other comprehensive income (loss) net of tax			171,300	(105,200)
Ending balance, Accumulated other comprehensive income	$ 83,900	$ (152,200)	$ 83,900	$ (152,200)