Supplemental Balance Sheet and Income Statement Information - Accumulated Other Comp Inc (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Changes in accumulated other comprehensive income (loss)
Balance at the beginning of the period			$ 1,151,384
Other comprehensive income (loss), net of tax	$ 2,132	$ 6,818	2,500	$ (10,400)
Balance at the end of the period	818,919		818,919
Accumulated Other Comprehensive Income
Changes in accumulated other comprehensive income (loss)
Balance at the beginning of the period			(11,124)	(11,788)
Other comprehensive income (loss) before reclassifications			2,420	(10,694)
Amounts reclassified from accumulated other comprehensive income (loss)			80	294
Other comprehensive income (loss), net of tax			2,500	(10,400)
Balance at the end of the period	(8,624)	(22,188)	(8,624)	(22,188)
Gains (losses) on cash flow hedges
Changes in accumulated other comprehensive income (loss)
Balance at the beginning of the period			2	(65)
Amounts reclassified from accumulated other comprehensive income (loss)				214
Other comprehensive income (loss), net of tax				214
Balance at the end of the period	2	149	2	149
Defined benefit pension plan items
Changes in accumulated other comprehensive income (loss)
Balance at the beginning of the period			(3,616)	(3,778)
Other comprehensive income (loss) before reclassifications			(1,900)
Amounts reclassified from accumulated other comprehensive income (loss)			80	80
Other comprehensive income (loss), net of tax			(1,820)	80
Balance at the end of the period	(5,436)	(3,698)	(5,436)	(3,698)
Foreign currency items
Changes in accumulated other comprehensive income (loss)
Balance at the beginning of the period			(7,510)	(7,945)
Other comprehensive income (loss) before reclassifications			4,320	(10,694)
Other comprehensive income (loss), net of tax			4,320	(10,694)
Balance at the end of the period	$ (3,190)	$ (18,639)	$ (3,190)	$ (18,639)