CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interest
Beginning Balance at Dec. 31, 2012	$ 1,557,323	$ 860	$ 116,720	$ 1,463,277	$ (39,064)	$ 15,530
Beginning Balance (in shares) at Dec. 31, 2012		85,988,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	313,084			311,372		1,712
Currency translation adjustment	(19,160)				(17,718)	(1,442)
Change in qualifying cash flow hedge, net of tax	314				314
Issuance of common stock for exercise of options, restricted stock units and employee stock purchases (in shares)		973,000
Issuance of common stock for exercise of options, restricted stock units and employee stock purchases	48,001	10	47,991
Purchase/ cancellation of treasury stock (in shares)		(1,461,000)
Purchase/ cancellation of treasury stock	(163,700)	(15)	0	(163,685)
Stock compensation expense	17,457		17,457
Excess tax benefit of stock options exercised	17,153		17,153
Noncontrolling interests attributable to acquisitions	4,211					4,211
Reduction to noncontrolling interests due to additional ownership	(7,137)		(4,211)			(2,926)
Payments to noncontrolling interests	(8)					(8)
Ending Balance at Dec. 31, 2013	1,767,538	855	195,110	1,610,964	(56,468)	17,077
Ending Balance (in shares) at Dec. 31, 2013	85,500,037	85,500,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	162,447			161,085		1,362
Currency translation adjustment	10,775				10,906	(131)
Change in qualifying cash flow hedge, net of tax	8				8
Issuance of common stock for exercise of options, restricted stock units and employee stock purchases (in shares)		467,000
Issuance of common stock for exercise of options, restricted stock units and employee stock purchases	25,744	5	25,739
Purchase/ cancellation of treasury stock (in shares)	(1,213,233)	(1,213,000)
Purchase/ cancellation of treasury stock	(137,186)	(12)	0	(137,174)
Stock compensation expense	9,124		9,124
Excess tax benefit of stock options exercised	7,080		7,080
Noncontrolling interests attributable to acquisitions	6,943					6,943
Reduction to noncontrolling interests due to additional ownership	(130)					(130)
Ending Balance at Jun. 30, 2014	$ 1,852,343	$ 848	$ 237,053	$ 1,634,875	$ (45,554)	$ 25,121
Ending Balance (in shares) at Jun. 30, 2014	84,753,696	84,754,000