Retirement Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Plan contributions	$ 104		$ 209
U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	97	$ 134	177	$ 240
Interest cost	415	423	830	855
Expected return on plan assets	(603)	(655)	(1,200)	(1,307)
Amortization of net actuarial loss	8	192	17	418
Amortization of prior service cost	10	10	21	21
Foreign currency	0	0	0	0
Net periodic (benefit) cost	(73)	104	(155)	227
Non-U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	36	36	72	72
Interest cost	103	125	208	248
Expected return on plan assets	(97)	(146)	(194)	(290)
Amortization of net actuarial loss	0	0	0	0
Amortization of prior service cost	32	65	64	130
Foreign currency	(16)	118	24	35
Net periodic (benefit) cost	58	198	174	195
Postretirement Medical Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans
Plan contributions	185		464
Service cost	24	17	48	48
Interest cost	100	87	199	196
Expected return on plan assets	0	0	0	0
Amortization of net actuarial loss	0	(35)	0	0
Amortization of prior service cost	0	0	0	0
Foreign currency	0	0	0	0
Net periodic (benefit) cost	$ 124	$ 69	$ 247	$ 244