Interim Consolidated Financial Statements - Revised Consolidated Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Current Assets:
Prepaid expenses and other current assets	$ 18,645	$ 18,978
Total current assets	221,723	336,697
Other assets	11,166	8,809
Total assets	368,828	487,650
Current Liabilities:
Deferred revenue	125,787	150,495
Total current liabilities	151,889	181,345
Total liabilities	160,861	190,778
Retained earnings	118,814	117,450
Total stockholders' equity	207,967	296,872
Total liabilities and stockholders' equity	368,828	487,650
As Previously Reported [Member]
Current Assets:
Prepaid expenses and other current assets		18,846
Total current assets		336,565
Other assets		9,123
Total assets		487,832
Current Liabilities:
Deferred revenue		150,479
Total current liabilities		181,329
Total liabilities		190,762
Retained earnings		117,648
Total stockholders' equity		297,070
Total liabilities and stockholders' equity		487,832
Adjustments [Member]
Current Assets:
Prepaid expenses and other current assets		132
Total current assets		132
Other assets		(314)
Total assets		(182)
Current Liabilities:
Deferred revenue		16
Total current liabilities		16
Total liabilities		16
Retained earnings		(198)
Total stockholders' equity		(198)
Total liabilities and stockholders' equity		(182)
As Revised [Member]
Current Assets:
Prepaid expenses and other current assets		18,978
Total current assets		336,697
Other assets		8,809
Total assets		487,650
Current Liabilities:
Deferred revenue		150,495
Total current liabilities		181,345
Total liabilities		190,778
Retained earnings		117,450
Total stockholders' equity		296,872
Total liabilities and stockholders' equity		$ 487,650