CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Additional Paid-in Capital	Retained Earnings (Accumulated Deficit)	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Common Class A	Common Stock	Restricted Stock [Member]
Balance at Dec. 31, 2014	$ 2,550,251	$ 2,450,782	$ 216,644	$ (169,530)	$ 52,251	$ 2	$ 102
Balance (shares) at Dec. 31, 2014				(2,018,000)		1,973,000	102,475,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Common Stock in connection with exercise of stock options	215,462	215,460					$ 2
Issuance of Common Stock in connection with exercise of stock options (shares)							2,457,000
Common Stock tendered upon exercise of stock options in connection with employee tax obligations	(160,538)	(160,538)
Common Stock tendered upon exercise of stock options in connection with employee tax obligations (in shares)							(298,000)
Issuance of Common Stock in connection with conversion of convertible senior notes	818,360	818,358					$ 2
Issuance of Common Stock in connection with conversion of convertible senior notes (in shares)							1,625,000
Issuance of Common Stock in connection with Company 401(k) Savings Plan contribution	15,382	15,382
Issuance of Common Stock in connection with Company 401(k) Savings Plan contribution (shares)							31,000
Issuance of restricted Common Stock under Long-Term Incentive Plan	0
Issuance of restricted Common Stock under Long-Term Incentive Plan (shares)								28,000
Conversion of Class A Stock to Common Stock (shares)						(60,000)	60,000
Stock-based compensation charges	464,022	464,022
Excess tax benefit from stock-based compensation	405,317	405,317
Acquisition of Common Stock in connection with exercise of convertible note hedges	0	136,539		$ (136,539)
Acquisition of Common Stock in connection with exercise of convertible note hedges (in shares)				(1,625,088)
Reduction of warrants	(449,456)	(449,456)
Reclassification of warrant liability	23,317	23,317
Reduction of equity component of convertible senior notes	(819,657)	(819,657)
Net income	636,056		636,056
Other Comprehensive Income (Loss), Net of Tax	(43,679)				(43,679)
Balance at Dec. 31, 2015	3,654,837	3,099,526	852,700	$ (306,069)	8,572	$ 2	$ 106
Balance (shares) at Dec. 31, 2015				(3,643,000)		1,913,000	106,378,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Common Stock in connection with exercise of stock options	115,182	115,180					$ 2
Issuance of Common Stock in connection with exercise of stock options (shares)							1,697,000
Common Stock tendered upon exercise of stock options in connection with employee tax obligations	(143,182)	(143,182)
Common Stock tendered upon exercise of stock options in connection with employee tax obligations (in shares)							(382,000)
Issuance of Common Stock in connection with conversion of convertible senior notes	48,004	48,004
Issuance of Common Stock in connection with conversion of convertible senior notes (in shares)							121,000
Issuance of Common Stock in connection with Company 401(k) Savings Plan contribution	16,561	16,561
Issuance of Common Stock in connection with Company 401(k) Savings Plan contribution (shares)							27,000
Issuance of restricted Common Stock under Long-Term Incentive Plan	0
Issuance of restricted Common Stock under Long-Term Incentive Plan (shares)								17,000
Conversion of Class A Stock to Common Stock (shares)						(2,000)	2,000
Stock-based compensation charges	574,887	574,887
Acquisition of Common Stock in connection with exercise of convertible note hedges	0	10,171		$ (10,171)
Acquisition of Common Stock in connection with exercise of convertible note hedges (in shares)				(121,048)
Reduction of warrants	(643,365)	(643,365)
Reduction of equity component of convertible senior notes	(47,789)	(47,789)
Net income	895,522		895,522
Other Comprehensive Income (Loss), Net of Tax	(21,412)				(21,412)
Balance at Dec. 31, 2016	4,449,245	3,029,993	1,748,222	$ (316,240)	(12,840)	$ 2	$ 108
Balance (shares) at Dec. 31, 2016				(3,764,000)		1,911,000	107,860,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Common Stock in connection with exercise of stock options	240,580	240,578					$ 2
Issuance of Common Stock in connection with exercise of stock options (shares)							2,249,000
Common Stock tendered upon exercise of stock options in connection with employee tax obligations	(201,621)	(201,621)
Adjustments related to tax withholding for share based compensation, restricted stock	100,067	100,067
Common Stock tendered upon exercise of stock options in connection with employee tax obligations (in shares)							(481,000)	(259,000)
Issuance of Common Stock in connection with Company 401(k) Savings Plan contribution	19,416	19,416
Issuance of Common Stock in connection with Company 401(k) Savings Plan contribution (shares)							45,000
Issuance of restricted Common Stock under Long-Term Incentive Plan	0
Issuance of restricted Common Stock under Long-Term Incentive Plan (shares)								63,000
Stock-based compensation charges	524,534	524,534
Net income	1,198,511		1,198,511
Other Comprehensive Income (Loss), Net of Tax	13,480				13,480
Balance at Dec. 31, 2017	$ 6,144,078	$ 3,512,833	$ 2,946,733	$ (316,240)	$ 640	$ 2	$ 110
Balance (shares) at Dec. 31, 2017				(3,764,000)		1,911,000	109,477,000