Consolidated Statements of Changes in Stockholders' Equity - USD ($)	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]	Class A Non-Voting Common Stock [Member]
Beginning balance at Dec. 31, 2012	$ 1,075,503,000	$ 781,000	$ 853,455,000	$ 175,554,000	$ 51,518,000	$ (5,819,000)	$ 14,000
Beginning balance, shares at Dec. 31, 2012		78,141,000					1,429,000
Net income	117,895,000			117,895,000
Foreign exchange translation adjustment	(21,144,000)				(21,144,000)
Stock-based compensation expense	8,386,000		8,386,000
Exercise of options	27,817,000	$ 23,000	27,781,000				$ 13,000
Exercise of options, shares		2,312,000					1,275,000
Income tax benefit related to exercise of stock options	24,194,000		24,194,000
Issuance of common stock, shares		25,000
Purchase of common stock	(943,000)					(943,000)
Ending balance at Dec. 31, 2013	1,231,708,000	$ 804,000	913,816,000	293,449,000	30,374,000	(6,762,000)	$ 27,000
Ending balance, shares at Dec. 31, 2013		80,478,000					2,704,000
Net income	131,127,000			131,127,000
Foreign exchange translation adjustment	(45,495,000)				(45,495,000)
Stock-based compensation expense	11,483,000		11,483,000
Exercise of options	24,110,000	$ 18,000	24,092,000
Exercise of options, shares		1,790,000
Income tax benefit related to exercise of stock options	15,454,000		15,454,000
Cash dividends declared - [$-value] per share (Note 4)	(10,494,000)			(10,494,000)
Purchase of common stock	(11,223,000)					(11,223,000)
Ending balance at Dec. 31, 2014	$ 1,346,670,000	$ 822,000	964,845,000	414,082,000	(15,121,000)	(17,985,000)	$ 27,000
Ending balance, shares at Dec. 31, 2014	82,268,722	82,268,000					2,703,846
Net income	$ 42,862,000			42,862,000
Foreign exchange translation adjustment	(68,049,000)				(68,049,000)
Stock-based compensation expense	43,746,000		43,746,000
Exercise of options	23,153,000	$ 22,000	23,131,000
Exercise of options, shares		2,207,000
Income tax benefit related to exercise of stock options	32,960,000		32,960,000
Issuance of common stock	717,802,000	$ 122,000	717,680,000
Issuance of common stock, shares		12,077,000
Cash dividends declared - [$-value] per share (Note 4)	(45,451,000)			(45,451,000)
Purchase of common stock	0
Ending balance at Dec. 31, 2015	$ 2,105,446,000	$ 966,000	1,794,115,000	$ 411,493,000	$ (83,170,000)	$ (17,985,000)	$ 27,000
Ending balance, shares at Dec. 31, 2015	96,552,226	96,552,000					2,703,846
Non-cash purchase price consideration (Note 11)	$ 11,753,000		$ 11,753,000