CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interest
Beginning Balance (in shares) at Dec. 31, 2013		85,500,000
Beginning Balance at Dec. 31, 2013	$ 1,767,538	$ 855	$ 195,110	$ 1,610,964	$ (56,468)	$ 17,077
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	328,146			326,456		1,690
Currency translation adjustment	(82,871)				(80,221)	(2,650)
Change in qualifying cash flow hedge, net of tax	(1,730)				(1,730)
Issuance of common stock for exercise of options, restricted stock units and employee stock purchases (in shares)		1,061,000
Issuance of common stock for exercise of options, restricted stock units and employee stock purchases	58,562	$ 11	58,551
Purchase and cancellation of treasury stock (in shares)		(1,677,000)
Purchase and cancellation of treasury stock	(194,066)	$ (17)	0	(194,049)
Stock compensation expense	17,773		17,773
Excess tax benefit of stock options exercised	17,906		17,906
Noncontrolling interests attributable to acquisitions	6,781					6,781
Reduction to noncontrolling interests due to additional ownership	$ (854)		(129)			(725)
Ending Balance (in shares) at Dec. 31, 2014	84,883,517	84,884,000
Ending Balance at Dec. 31, 2014	$ 1,917,185	$ 849	289,211	1,743,371	(138,419)	22,173
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	136,706			135,907		799
Currency translation adjustment	(39,941)				(38,890)	(1,051)
Change in qualifying cash flow hedge, net of tax	(3,598)				(3,598)
Issuance of common stock for exercise of options, restricted stock units and employee stock purchases (in shares)		615,000
Issuance of common stock for exercise of options, restricted stock units and employee stock purchases	$ 43,630	$ 5	43,625
Purchase and cancellation of treasury stock (in shares)	(675,520)	(676,000)
Purchase and cancellation of treasury stock	$ (91,161)	$ (6)	0	(91,155)
Stock compensation expense	10,904		10,904
Excess tax benefit of stock options exercised	10,899		10,899
Reduction to noncontrolling interests due to additional ownership	$ (2,603)		0			(2,603)
Ending Balance (in shares) at Jun. 30, 2015	84,823,229	84,823,000
Ending Balance at Jun. 30, 2015	$ 1,982,021	$ 848	$ 354,639	$ 1,788,123	$ (180,907)	$ 19,318