Condensed Consolidating Balance Sheets (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Dec. 31, 2011 As Restated [Member]	Mar. 31, 2011 As Restated [Member]	Dec. 31, 2010 As Restated [Member]	Mar. 31, 2012 Parent [Member]	Dec. 31, 2011 Parent [Member]	Dec. 31, 2011 Parent [Member] As Restated [Member]	Mar. 31, 2011 Parent [Member] As Restated [Member]	Dec. 31, 2010 Parent [Member] As Restated [Member]	Mar. 31, 2012 Guarantor Subsidiaries [Member]	Dec. 31, 2011 Guarantor Subsidiaries [Member]	Dec. 31, 2011 Guarantor Subsidiaries [Member] As Restated [Member]	Mar. 31, 2011 Guarantor Subsidiaries [Member] As Restated [Member]	Dec. 31, 2010 Guarantor Subsidiaries [Member] As Restated [Member]	Mar. 31, 2012 Non-Guarantor Subsidiaries [Member]	Dec. 31, 2011 Non-Guarantor Subsidiaries [Member]	Dec. 31, 2011 Non-Guarantor Subsidiaries [Member] As Restated [Member]	Mar. 31, 2011 Non-Guarantor Subsidiaries [Member] As Restated [Member]	Dec. 31, 2010 Non-Guarantor Subsidiaries [Member] As Restated [Member]	Mar. 31, 2012 Consolidation, Eliminations [Member]	Dec. 31, 2011 Consolidation, Eliminations [Member]	Dec. 31, 2011 Consolidation, Eliminations [Member] As Restated [Member]	Mar. 31, 2011 Consolidation, Eliminations [Member] As Restated [Member]	Dec. 31, 2010 Consolidation, Eliminations [Member] As Restated [Member]
Current Assets:
Cash and cash equivalents	$ 337,382	$ 285,512	$ 285,512	$ 227,180	$ 171,618	$ 150,225	$ 150,171	$ 150,171	$ 110,015	$ 46,012	$ 126,571	$ 93,285	$ 93,285	$ 73,625	$ 87,619	$ 60,586	$ 42,056	$ 42,056	$ 43,540	$ 37,987	$ 0	$ 0	$ 0	$ 0	$ 0
Restricted cash	3,315	8,733	8,733			0		0			3,113		8,515			202		218			0		0
Accounts receivable, net	131,953	114,778	114,778			0		0			108,096		89,656			23,857		25,122			0		0
Deferred tax assets—current portion	33,412	32,063	32,063			0		0			28,951		27,543			4,461		4,520			0		0
Prepaid expenses and other current assets	27,117	24,584	24,584			2,499		9,362			15,388		45			9,230		15,177			0		0
Total current assets	533,179	465,670	465,670			152,724		159,533			282,119		219,044			98,336		87,093			0		0
Non-Current Assets:
Restricted cash	712	652	652			0		0			0		0			712		652			0		0
Property and equipment, net	52,158	52,541	52,541			0		0			45,271		45,920			6,887		6,621			0		0
Goodwill	231,377	231,377	231,377			0		0			231,377		231,377			0		0			0		0
Other intangibles, net	130,650	141,882	141,882			0		0			130,650		141,882			0		0			0		0
Deferred tax assets—long-term portion	256,344	258,271	258,271			0		0			250,496		252,469			5,848		5,802			0		0
Other non-current assets	20,491	20,565	20,565			5,057		5,536			1,052		1,047			14,382		13,982			0		0
Investment in subsidiaries	0		0			247,271		235,908			15,774		41,030			0		0			(263,045)		(276,938)
Intercompany accounts	0		0			581,370		568,429			(576,189)		(580,202)			(5,181)		11,773			0		0
Total non-current assets	691,732	705,288	705,288			833,698		809,873			98,431		133,523			22,648		38,830			(263,045)		(276,938)
Total Assets	1,224,911	1,170,958	1,170,958			986,422		969,406			380,550		352,567			120,984		125,923			(263,045)		(276,938)
Current Liabilities:
Accounts payable	8,378	7,740	7,740			0		0			6,700		5,954			1,678		1,786			0		0
Accrued expenses and other liabilities	76,226	73,111	73,111			7,252		5,023			39,813		36,986			29,161		31,102			0		0
Deferred revenue—current portion	142,636	108,217	108,217			0		0			125,355		84,237			17,281		23,980			0		0
Total current liabilities	227,240	189,068	189,068			7,252		5,023			171,868		127,177			48,120		56,868			0		0
Non-Current Liabilities:
Long-term debt	273,347	273,210	273,210			273,347		273,210			0		0			0		0			0		0
Accrued exit and disposal obligations	3,595	3,926	3,926			0		0			920		1,142			2,675		2,784			0		0
Liability for uncertain tax positions	4,144	4,098	4,098			0		0			1,704		1,645			2,440		2,453			0		0
Deferred revenue—long-term portion	7,402	8,115	8,115			0		0			7,109		7,804			293		311			0		0
Other non-current liabilities	3,360	1,368	1,368			0		0			2,940		588			420		780			0		0
Total non-current liabilities	291,848	290,717	290,717			273,347		273,210			12,673		11,179			5,828		6,328			0		0
Total Liabilities	519,088	479,785	479,785			280,599		278,233			184,541		138,356			53,948		63,196			0		0
Stockholders’ Equity	705,823	691,173	691,173			705,823		691,173			196,009		214,211			67,036		62,727			(263,045)		(276,938)
Total Liabilities and Stockholders’ Equity	$ 1,224,911	$ 1,170,958	$ 1,170,958			$ 986,422		$ 969,406			$ 380,550		$ 352,567			$ 120,984		$ 125,923			$ (263,045)		$ (276,938)