Pension and Other Postretirement Benefits - Change in Benefit Obligation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Benefits
Change in benefit obligation:
Benefit obligation, beginning of year	$ (412,880)	$ (266,515)
Service cost	(3,668)	(4,579)	$ (4,767)
Interest cost	(12,261)	(11,480)	(7,551)
Participant contributions	(86)	(85)
Actuarial gain (loss)	(39,329)	14,968
Acquisitions	0	(185,692)
Settlements	49	7,054
Plan amendments	0	(2,822)
Foreign currency exchange rate changes	(9,890)	23,439
Benefits paid	16,713	12,832
Benefit obligation, end of year	(461,352)	(412,880)	(266,515)
Other Benefits
Change in benefit obligation:
Benefit obligation, beginning of year	(26,143)	(30,333)
Service cost	(35)	(47)	(49)
Interest cost	(960)	(945)	(1,139)
Participant contributions	(4)	(6)
Actuarial gain (loss)	(2,374)	1,681
Acquisitions	0	0
Settlements	0	0
Plan amendments	0	0
Foreign currency exchange rate changes	(1,260)	2,020
Benefits paid	1,306	1,487
Benefit obligation, end of year	$ (29,470)	$ (26,143)	$ (30,333)