CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Statement of Comprehensive Income [Abstract]
Net income including non-controlling interests	$ 70,876	$ 77,289	$ 139,194	$ 133,713
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) on derivatives designated and qualifying as cash flow hedges, net of tax of $160 and $218 in the three and six months ended June 30, 2015; $90 and $184 in the three and six months ended June 30, 2014	(579)	(176)	521	(597)
Defined benefit pension plan activity, net of tax of $1,975 and $4,370 in the three and six months ended June 30, 2015; $1,423 and $3,261 in the three and six months ended June 30, 2014	3,571	2,536	7,109	5,080
Currency translation adjustment	15,150	12,130	(41,402)	(228)
Other comprehensive income (loss):	18,142	14,490	(33,772)	4,255
Comprehensive income	89,018	91,779	105,422	137,968
Comprehensive income (loss) attributable to non-controlling interests	5	(19)	(572)	633
Comprehensive income attributable to shareholders	$ 89,013	$ 91,798	$ 105,994	$ 137,335