CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income including non-controlling interests	$ 31,309	$ 70,876	$ 84,933	$ 139,194
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) on derivatives designated and qualifying as cash flow hedges, net of tax of $207 and $4 in the three and six months ended June 30, 2016; $160 and $218 in the three and six months ended June 30, 2015	(645)	(579)	191	521
Defined benefit pension plan activity, net of tax of $1,132 and $2,043 in the three and six months ended June 30, 2016; $1,975 and $4,370 in the three and six months ended June 30, 2015	2,617	3,571	4,235	7,109
Currency translation adjustment	(18,997)	15,150	5,252	(41,402)
Other comprehensive income (loss):	(17,025)	18,142	9,678	(33,772)
Comprehensive income	14,284	89,018	94,611	105,422
Comprehensive income (loss) attributable to non-controlling interests	(58)	5	(57)	(572)
Comprehensive income attributable to shareholders	$ 14,342	$ 89,013	$ 94,668	$ 105,994