COMPREHENSIVE INCOME (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010
Components of comprehensive income:
Net income, as reported	$ 82,392,000	$ 66,496,000	$ 221,683,000	$ 162,897,000
Other comprehensive income (loss):
Change in unrealized loss on available-for-sale securities, net of tax		181,000	1,478,000	3,330,000
Foreign currency translation adjustments	(3,509,000)	3,119,000	(3,263,000)	452,000
Comprehensive income	78,883,000	69,796,000	219,898,000	166,679,000
Components of accumulated other comprehensive (loss) income:
Accumulated net unrealized loss on available-for-sale securities, net of tax benefit $1.0 million as of December 31, 2010					(1,478,000)
Tax benefit					1,000,000
Foreign currency translation adjustments	(1,504,000)		(1,504,000)		1,759,000
Total accumulated other comprehensive income	$ (1,504,000)		$ (1,504,000)		$ 281,000