Deferred Tax Assets and Liabilities Result from Differences in Timing of Recognition of Certain Income and Expense Items for Tax and Financial Accounting Purposes (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Total current deferred tax assets	$ 28,484	$ 13,351
Less: valuation allowance	(2,540)	(1,034)
Net current deferred tax assets	25,944	12,317
Total noncurrent deferred tax assets	27,600	44,376
Noncurrent deferred tax liabilities
Depreciation and amortization	(8,539)	(9,415)
Total noncurrent deferred tax liabilities	(8,539)	(9,415)
Less: valuation allowance	(5,595)	(6,818)
Net noncurrent deferred tax assets	13,466	28,143
Current Assets
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Allowance for uncollectible accounts	1,184	1,414
Deferred revenue	9,170	4,622
Alliance deferred costs	8,287	(203)
Deferred acquisition costs	2,480
Compensation	6,364	6,268
Other	999	1,250
Noncurrent Assets
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Foreign tax credits	2,260	6,706
General business credits	125	1,246
Stock based compensation	12,785	9,921
Foreign net operating loss carryforwards	3,217	4,612
Capital loss carryforwards	3,221	3,259
Deferred revenue	3,913	8,394
Alliance deferred costs	87	9,962
U.S. net operating loss carryforwards	1,783
Other	$ 209	$ 276