Pension and Other Postretirement Benefits - Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Pension Benefits
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), before Tax [Abstract]
Net actuarial loss (gain), beginning of year	$ 44,359
Amortization of actuarial gain (loss)	(2,810)
Actuarial gain	(15,032)
Asset loss	24,755
Settlement loss recognized	(1,342)		$ (7,600)
Currency impact	(1,464)
Net actuarial loss (gain), end of year	48,466	$ 44,359
Prior service cost, beginning of year	11
Amortization of prior service credit	42	41	42
Prior service cost occurring during the year	2,822
Currency impact	(141)
Prior service cost, end of year	2,734	11
Other Benefits
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), before Tax [Abstract]
Net actuarial loss (gain), beginning of year	(1,545)
Amortization of actuarial gain (loss)	12
Actuarial gain	(1,681)
Asset loss	0
Settlement loss recognized	0
Currency impact	167
Net actuarial loss (gain), end of year	(3,047)	(1,545)
Prior service cost, beginning of year	0
Amortization of prior service credit	0	0	$ 42
Prior service cost occurring during the year	0
Currency impact	0
Prior service cost, end of year	$ 0	$ 0