CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net income including non-controlling interests	$ 286,993	$ 247,475	$ 198,373
Unrealized gain on derivatives designated and qualifying as cash flow hedges, net of tax of $346 in 2018; $17 in 2017; $(21) in 2016	819	288	39
Defined pension plan activity, net of tax of $1,681 in 2018, $19,252 in 2017; $4,297 in 2016	3,228	10,662	3,837
Currency translation adjustment	(50,693)	71,016	(36,752)
Other comprehensive income (loss)	(46,646)	81,966	(32,876)
Comprehensive income	240,347	329,441	165,497
Comprehensive (loss) income attributable to non-controlling interests	(166)	87	(132)
Comprehensive income attributable to shareholders	240,513	329,354	165,629
Accumulated Other Comprehensive Income (Loss) [Member]
Unrealized gain on derivatives designated and qualifying as cash flow hedges, net of tax of $346 in 2018; $17 in 2017; $(21) in 2016	819	288	39
Defined pension plan activity, net of tax of $1,681 in 2018, $19,252 in 2017; $4,297 in 2016	3,228	10,662	3,837
Currency translation adjustment	$ (50,600)	$ 70,901	$ (36,646)