Employee Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Defined benefit plans:
Multiemployer pension plans	$ 498	$ 494	$ 1,481	$ 1,520
Defined contribution pension plans	3,278	2,291	8,306	7,593
U. S. Plans
Defined benefit plans:
Service cost	942	945	2,825	2,837
Interest cost	2,469	2,545	7,408	7,635
Expected return on plan assets	(3,552)	(3,601)	(10,656)	(10,803)
Recognized prior service costs	8	16	24	47
Recognized loss	1,425	1,373	4,276	4,117
Settlement/curtailment losses	0	223	0	223
Defined benefit pension plans net periodic pension cost (income)	1,292	1,501	3,877	4,056
Defined benefit pension plan	4,112	471	5,054	1,411
Anticipated contributions to defined benefit pension plans during the remainder of the fiscal year			800
International Plans
Defined benefit plans:
Service cost	426	405	1,243	1,214
Interest cost	5,843	6,542	17,349	20,649
Expected return on plan assets	(10,632)	(10,475)	(31,571)	(33,157)
Recognized prior service costs	48	44	139	133
Recognized loss	4,130	2,923	12,260	9,283
Settlement/curtailment losses	0	0	0	0
Defined benefit pension plans net periodic pension cost (income)	(185)	(561)	(580)	(1,878)
Defined benefit pension plan	$ 3,038	$ 3,170	14,338	$ 16,222
Anticipated contributions to defined benefit pension plans during the remainder of the fiscal year			$ 3,200