CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $) In Thousands, unless otherwise specified	Total	Class A Stock	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Balance at Dec. 31, 2011	$ 485,732	$ 2	$ 91	$ 1,754,824	$ (1,267,323)	$ (1,862)
Balance (shares) at Dec. 31, 2011		2,109	90,692
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Common Stock in connection with exercise of stock options	39,634		3	39,631
Issuance of Common Stock in connection with exercise of stock options (shares)			3,234
Common Stock tendered upon exercise of stock options in connection with employee tax obligations	(61,444)			(61,444)
Common Stock tendered upon exercise of stock options in connection with employee tax obligations (shares)			(568)
Issuance of Common Stock in connection with Company 401(k) Savings Plan contribution
Issuance of Common Stock in connection with Company 401(k) Savings Plan contribution (shares)			64
Issuance of restricted Common Stock under Long-Term Incentive Plan			500
Conversion of Class A Stock to Common Stock (shares)		(20)	20
Stock-based compensation charges	42,850			42,850
Net income	88,394				88,394
Other comprehensive income (loss), net of tax	(509)					(509)
Balance at Jun. 30, 2012	594,657	2	94	1,775,861	(1,178,929)	(2,371)
Balance (shares) at Jun. 30, 2012		2,089	93,942
Balance at Dec. 31, 2012	1,245,385	2	95	1,763,508	(517,054)	(1,166)
Balance (shares) at Dec. 31, 2012		2,069	95,223
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Common Stock in connection with exercise of stock options	30,498		2	30,496
Issuance of Common Stock in connection with exercise of stock options (shares)			1,661
Common Stock tendered upon exercise of stock options in connection with employee tax obligations	(73,137)			(73,137)
Common Stock tendered upon exercise of stock options in connection with employee tax obligations (shares)			(290)
Issuance of Common Stock in connection with Company 401(k) Savings Plan contribution
Issuance of Common Stock in connection with Company 401(k) Savings Plan contribution (shares)			38
Conversion of Class A Stock to Common Stock (shares)		(30)	30
Stock-based compensation charges	98,728			98,728
Excess tax benefit from stock-based compensation	7,876			7,876
Net income	186,250				186,250
Other comprehensive income (loss), net of tax	(2,263)					(2,263)
Balance at Jun. 30, 2013	$ 1,493,337	$ 2	$ 97	$ 1,827,471	$ (330,804)	$ (3,429)
Balance (shares) at Jun. 30, 2013		2,039	96,662