Employee Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Defined benefit plans:
Multiemployer pension plans	$ 519	$ 498	$ 1,020	$ 983
Defined contribution pension plans	2,747	2,468	5,582	5,028
Pension Plan | U.S. Plans
Defined benefit plans:
Service cost	11	11	21	22
Interest cost	2,390	2,470	4,781	4,939
Expected return on plan assets	(3,017)	(2,621)	(6,034)	(5,242)
Recognized prior service costs	0	8	0	16
Recognized loss	1,302	1,425	2,604	2,850
Settlement/curtailment losses			166	0
Defined benefit pension plans net periodic pension cost (income)	686	1,293	1,538	2,585
Defined benefit pension plan	2,067	471	3,351	942
Anticipated contributions to defined benefit pension plans during the remainder of the fiscal year	6,600		6,600
Pension Plan | International Plans
Defined benefit plans:
Service cost	408	406	794	817
Interest cost	5,442	5,773	11,114	11,507
Expected return on plan assets	(10,696)	(10,515)	(21,841)	(20,939)
Recognized prior service costs	(37)	46	(76)	91
Recognized loss	3,690	4,087	7,530	8,129
Settlement/curtailment losses			0	0
Defined benefit pension plans net periodic pension cost (income)	(1,193)	(203)	(2,479)	(395)
Defined benefit pension plan	3,239	$ 2,963	12,973	$ 11,300
Anticipated contributions to defined benefit pension plans during the remainder of the fiscal year	$ 5,600		$ 5,600