Pension and Other Postretirement Benefits - Change in Benefit Obligation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Pension Benefits
Change in benefit obligation:
Benefit obligation, beginning of year	$ (272,025)	$ (256,481)
Service cost	(4,705)	(4,978)	$ (4,981)
Interest cost	(11,690)	(7,671)	(8,909)
Participant contributions	(85)	(91)
Actuarial gain (loss)	15,032	(3,291)
Divestitures (acquisitions)	(185,692)	794
Settlements	7,437	49
Plan amendments	(2,822)	0
Foreign currency exchange rate changes	23,454	(14,299)
Benefits paid	12,849	13,943
Benefit obligation, end of year	(418,247)	(272,025)	(256,481)
Other Benefits
Change in benefit obligation:
Benefit obligation, beginning of year	(30,333)	(32,038)
Service cost	(47)	(49)	(46)
Interest cost	(945)	(1,139)	(1,259)
Participant contributions	(6)	(7)
Actuarial gain (loss)	1,681	3,370
Divestitures (acquisitions)	0	0
Settlements	0	0
Plan amendments	0	0
Foreign currency exchange rate changes	2,020	(2,022)
Benefits paid	1,487	1,552
Benefit obligation, end of year	$ (26,143)	$ (30,333)	$ (32,038)