Pension and Other Postretirement Benefits - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension and Other Postretirement Benefits [Abstract]
Value of Employer Securities Included in Plan Assets	$ 1,500	$ 1,300
Defined Benefit Plan Disclosure [Line Items]
Prior Service Cost Charge	$ 4,000
Description of Defined Contribution Plan	The Company has a 401(k) plan with an employer match covering a majority of its domestic employees. The plan allows for and the Company previously paid a nonelective contribution on behalf of participants who have completed one year of service equal to 3% of the eligible participants’ compensation in the form of Company common stock.
Non-elective Match Percentage	3.00%
Total Contribution Amount	$ 2,900	2,700	$ 2,600
Defined Benefit Plan Explanation Of Significant Change In Benefit Obligation Or Plan Assets Not Apparent From Other Required Disclosures	During the second quarter of 2017, the Company’s U.S. pension plan offered a cash settlement to its vested terminated participants, which allowed them to receive the value of their pension benefits as a single lump sum payment. As payments from the U.S. pension plan for this cash out offering exceeded the service and interest cost components of the U.S. pension plan expense for the year ended December 31, 2017, the Company recorded a settlement charge of approximately $1.9 million. This settlement charge represented the immediate recognition into expense of a portion of the unrecognized loss within AOCI on the balance sheet in proportion to the share of the projected benefit obligation that was settled by these payments. The gross pension benefit obligation was reduced by approximately $4.0 million as a result of these payments.
Defined Benefit Plan Other Costs	$ 4,000
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	176,300	167,100
Domestic [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	$ 62,200	$ 66,700
Commingled Fund Asset Allocation	As of December 31, 2017, the U.S. pension plan commingled funds included approximately 60 percent of investments in equity securities and 40 percent of investments in fixed income securities.
Percentage of domestic pension assets	3.00%	3.00%
Net Periodic Benefit Cost	$ 3,607	$ 1,495	1,754
Domestic [Member] | Other Postretirement Benefit Plans Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Net Periodic Benefit Cost	206	152	295
Domestic [Member] | Supplemental Employee Retirement Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Net Periodic Benefit Cost	1,400	900	900
Foreign [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	$ 114,100	100,400
Commingled Fund Asset Allocation	As of December 31, 2017, foreign pension plan commingled funds included approximately 31 percent of investments in equity securities, 57 percent of investments in fixed income securities, and 12 percent of other non-related investments, primarily real estate.
Net Periodic Benefit Cost	$ 3,986	$ 3,341	$ 4,325