Consolidated Statements Of Shareholders' Deficit - USD ($) $ in Thousands	Common Stock [Member] Class A Common Stock [Member]	Additional Paid-In Capital [Member] Shares - Warrant [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive (Loss) Income, Net [Member]	Shares - Warrant [Member]	Total
BALANCE at Dec. 31, 2014	$ 1,291		$ 2,062,775	$ (2,542,380)	$ (182,486)		$ (660,800)
BALANCE, Shares at Dec. 31, 2014	129,134,000
Net income (loss)				(175,656)			(175,656)
Common stock issued in connection with stock purchase/option plans	$ 6		21,604				21,610
Common stock issued in connection with stock purchase/option plans, Shares	591,000
Non-cash stock compensation			29,208				29,208
Settlement of common stock warrants		$ (150,874)				$ (150,874)
Repurchase and retirement of common stock	$ (40)			(450,033)			(450,073)
Repurchase and retirement of common stock, Shares	(3,982,000)
Foreign currency translation adjustments					(319,559)		(319,559)
BALANCE at Dec. 31, 2015	$ 1,257		1,962,713	(3,168,069)	(502,045)		(1,706,144)
BALANCE, Shares at Dec. 31, 2015	125,743,000
Net income (loss)				76,238			76,238
Common stock issued in connection with stock purchase/option plans	$ 6		14,404				14,410
Common stock issued in connection with stock purchase/option plans, Shares	602,000
Non-cash stock compensation			33,403				33,403
Repurchase and retirement of common stock	$ (53)			(545,636)			(545,689)
Repurchase and retirement of common stock, Shares	(5,341,000)
Foreign currency translation adjustments					131,861		131,861
BALANCE at Dec. 31, 2016	$ 1,210		2,010,520	(3,637,467)	(370,184)		(1,995,921)
BALANCE, Shares at Dec. 31, 2016	121,004,000
Net income (loss)				103,654			103,654
Common stock issued in connection with stock purchase/option plans	$ 8		54,798				54,806
Common stock issued in connection with stock purchase/option plans, Shares	812,000
Non-cash stock compensation			38,844				38,844
Common stock issued in connection with acquisitions	$ 5		63,308				63,313
Common stock issued in connection with acquisitions, Shares	488,000
Repurchase and retirement of common stock	$ (59)			(854,475)			(854,534)
Repurchase and retirement of common stock, Shares	(5,858,000)
Foreign currency translation adjustments					(9,276)		(9,276)
BALANCE at Dec. 31, 2017	$ 1,164		$ 2,167,470	$ (4,388,288)	$ (379,460)		$ (2,599,114)
BALANCE, Shares at Dec. 31, 2017	116,446,000