Retirement and Benefit Plans - (Details)	12 Months Ended
	Dec. 31, 2017 USD ($) plan Times Participants yr	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Compensation and Retirement Disclosure [Abstract]
Company matching employee contributions	66.70%
Maximum percentage of matching contribution for total compensation	3.00%
Discretionary contributions, percentage of qualified wages	1.00%
Contribution expense	$ 2,131,000	$ 2,335,000	$ 2,573,000
Defined Benefit Plan Disclosure [Line Items]
Number of participants unaffected by plan conversion | Participants	3
Death benefit only plan, benefit payment as multiplier of final earnings | Times	1
Death benefit only plan, benefit payment as multiplier of final earnings, current employee | Times	3
Supplemental Executive Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Interest credited for active participants (as a percent)	0.00%
Accumulated benefit obligation	$ 6,027,000	$ 6,003,000
Assumption, future salary increase rate	3.25%
Assumed discount rate	3.60%	4.14%
Retirement age | yr	67
Projected benefit obligation	$ 6,027,000	$ 6,003,000
Interest (benefit) cost	246,000	908,000	42,000
Net periodic benefit (income) costs	414,000	1,073,000
Benefit payments	391,000	1,279,000	21,517,000
Death Benefit Only Plan
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income) costs	150,000	(121,000)	103,000
Service cost and accrual adjustments	$ (69,000)	(216,000)	(28,000)
Switzerland | Foreign Postretirement Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Number of plans | plan	2
Europe | Foreign Postretirement Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Amounts recognized in other comprehensive income (loss)	$ 436,000	$ 1,004,000	$ 19,000