Retirement Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Plan contributions	$ 79
U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	0	$ 80
Interest cost	390	415
Expected return on plan assets	(585)	(597)
Amortization of net actuarial loss	10	9
Amortization of prior service cost	0	11
Foreign currency	0	0
Net periodic (benefit) cost	(185)	(82)
Non-U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	24	36
Interest cost	90	105
Expected return on plan assets	(96)	(97)
Amortization of net actuarial loss	0	0
Amortization of prior service cost	47	32
Foreign currency	(5)	40
Net periodic (benefit) cost	60	116
Postretirement Medical Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans
Plan contributions	209
Service cost	20	24
Interest cost	91	99
Expected return on plan assets	0	0
Amortization of net actuarial loss	0	0
Amortization of prior service cost	0	0
Foreign currency	0	0
Net periodic (benefit) cost	$ 111	$ 123