CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income including non-controlling interests	$ 55,848	$ 53,624
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) on derivatives designated and qualifying as cash flow hedges, net of tax of $(431) and $(203) in the three months ended March 31, 2017 and 2016	1,524	836
Defined benefit pension plan activity, net of tax of $213 and $911 in the three months ended March 31, 2017 and 2016	714	1,618
Currency translation adjustment	28,533	24,249
Other comprehensive income (loss):	30,771	26,703
Comprehensive income (loss)	86,619	80,327
Comprehensive income (loss) attributable to non-controlling interests	26	1
Comprehensive income (loss) attributable to shareholders	$ 86,593	$ 80,326