Condensed Consolidating Statements of Cash Flows (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011 As Restated [Member]	Mar. 31, 2012 Parent [Member]	Mar. 31, 2011 Parent [Member] As Restated [Member]	Mar. 31, 2012 Guarantor Subsidiaries [Member]	Mar. 31, 2011 Guarantor Subsidiaries [Member] As Restated [Member]	Mar. 31, 2012 Non-Guarantor Subsidiaries [Member]	Mar. 31, 2011 Non-Guarantor Subsidiaries [Member] As Restated [Member]	Mar. 31, 2012 Consolidation, Eliminations [Member]	Mar. 31, 2011 Consolidation, Eliminations [Member] As Restated [Member]
Condensed Financial Statements, Captions [Line Items]
Net Cash Provided by (Used in) Operating Activities	$ 48,866	$ 59,216	$ (1,436)	$ 66,214	$ 30,074	$ (11,926)	$ 20,228	$ 4,928	$ 0	$ 0
Investing Activities:
Change in restricted cash	5,358	458	0	(11)	5,402	480	(44)	(11)	0	0
Payment of direct costs related to acquisitions		0
Purchase of property and equipment	(3,000)	(2,997)	0	0	(1,975)	(2,580)	(1,025)	(417)	0	0
Proceeds from disposal of property and equipment	139	26	0	0	5	26	134	0	0	0
Net cash (used in) provided by investing activities	2,497	(2,513)	0	(11)	3,432	(2,074)	(935)	(428)	0	0
Financing Activities:
Issuance of common stock—equity plans	1,780	2,678	1,780	2,678	0	0	0	0	0	0
Purchase of treasury stock	(290)	(3,222)	(290)	(3,222)	0	0	0	0	0	0
Debt issuance costs	0	(1,656)		(1,656)		0		0		0
Change in intercompany receivable/payable	0	0	0	0	(220)	6	220	(6)	0	0
Net cash (used in) provided by financing activities	1,490	(2,200)	1,490	(2,200)	(220)	6	220	(6)	0	0
Effect of exchange rates on cash and cash equivalents	(983)	1,059	0	0	0	0	(983)	1,059	0	0
Net increase (decrease) in cash and cash equivalent	51,870	55,562	54	64,003	33,286	(13,994)	18,530	5,553	0	0
Cash and Cash Equivalents, Beginning of Period	285,512	171,618	150,171	46,012	93,285	87,619	42,056	37,987	0	0
Cash and Cash Equivalents, End of Period	$ 337,382	$ 227,180	$ 150,225	$ 110,015	$ 126,571	$ 73,625	$ 60,586	$ 43,540	$ 0	$ 0