CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (USD $) In Thousands, except Share data	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interest
Beginning Balance at Dec. 31, 2010	$ 1,080,350	$ 852	$ 46,945	$ 1,017,497	$ (16,869)	$ 31,925
Beginning Balance (in shares) at Dec. 31, 2010		85,242,000
Net income	237,343			234,751		2,592
Currency translation adjustment	(32,893)				(29,456)	(3,437)
Amortization of treasury lock into income, net of tax of $54 and $216 for the three months ended March 31,2012 and for the year ended December 31,2011 respectively	341				341
Comprehensive income	204,791
Issuance of common stock for exercise of options and employee stock purchases (in shares)		1,016,000
Issuance of common stock for exercise of options and employee stock purchases	36,405	11	36,394
Purchase/ cancellation of treasury stock (in Shares)		(1,562,000)
Purchase/ cancellation of treasury stock	(124,056)	(16)	(115,095)	(8,945)
Stock compensation expense	15,367		15,367
Excess tax benefit of stock options exercised	17,410		17,410
Noncontrolling interests acquired from new acquisitions	10,708					10,708
Reduction to noncontrolling interests due to additional ownership	(11,231)		(1,021)			(10,210)
Reduction to noncontrolling interests due to divestiture	(1,959)					(1,959)
Payments to noncontrolling interests	(534)					(534)
Ending Balance at Dec. 31, 2011	1,227,251	847	0	1,243,303	(45,984)	29,085
Ending Balance (in shares) at Dec. 31, 2011	84,696,227	84,696,000
Net income	65,315			64,857		458
Currency translation adjustment	17,427				16,361	1,066
Amortization of treasury lock into income, net of tax of $54 and $216 for the three months ended March 31,2012 and for the year ended December 31,2011 respectively	85				85
Comprehensive income	82,827
Issuance of common stock for exercise of options and employee stock purchases (in shares)		336,000
Issuance of common stock for exercise of options and employee stock purchases	13,655	3	13,652
Purchase/ cancellation of treasury stock (in Shares)	(38,552)	(38,000)
Purchase/ cancellation of treasury stock	(2,945)	0	0	(2,945)
Stock compensation expense	4,085		4,085
Excess tax benefit of stock options exercised	5,061		5,061
Reduction to noncontrolling interests due to additional ownership	(2,196)					(2,196)
Ending Balance at Mar. 31, 2012	$ 1,327,738	$ 850	$ 22,798	$ 1,305,215	$ (29,538)	$ 28,413
Ending Balance (in shares) at Mar. 31, 2012	84,994,111	84,994,000