Income Taxes (Details) (USD $)	3 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Current:
Federal		$ 201,475,000	$ 0
State		23,489,000	4,308,000
Current Foreign Tax Expense (Benefit)		433,000	0
Total current tax expense (benefit)		225,397,000	4,308,000
Deferred:
Federal		54,910,000	(300,319,000)
State		8,700,000	(39,837,000)
Deferred Foreign Income Tax Expense (Benefit)		(9,000)	0
Total deferred tax expense (benefit)		63,601,000	(340,156,000)	0
Total income tax expense (benefit)	(335,800,000)	288,998,000	(335,848,000)	(1,132,000)
Income tax expense (benefit) resulting from provision in American Recovery and Reinvestment Act of 2009				(700,000)
Income tax expense (benefit) in connection with the net tax effect of unrealized gain on available-for-sale marketable securities				(400,000)
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]
U.S. federal statutory tax rate		35.00%	35.00%	35.00%
State and local income taxes		3.40%	5.40%
Change in state effective rate		0.00%	5.40%
Other non-deductible and permanent differences		2.10%	2.80%
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Percent		4.90%	0.00%
Effective Income Tax Rate Reconciliation, Tax Credit, Percent		(4.90%)	0.00%
Reclassification of net operating losses related to exercises of stock options		0.00%	9.30%
Provision (benefit) attributable to valuation allowances		0.00%	(139.00%)
Effective income tax rate		40.50%	(81.10%)
Deferred tax assets:
Net operating loss carry-forward	77,119,000	135,000	77,119,000
Fixed assets	1,380,000	18,902,000	1,380,000
Deferred revenue	99,659,000	88,033,000	99,659,000
Deferred compensation	53,367,000	109,715,000	53,367,000
Income tax credit carry-forwards	71,164,000	9,372,000	71,164,000
Capitalized research and development costs	24,437,000	18,942,000	24,437,000
Other	23,511,000	34,215,000	23,511,000
Deferred tax assets, gross	350,637,000	279,314,000	350,637,000
Valuation allowance	(2,486,000)	(1,830,000)	(2,486,000)
Deferred tax assets, net	348,151,000	277,484,000	348,151,000
Deferred tax liabilities:
Accruals	(6,824,000)	0	(6,824,000)
Convertible senior notes	(1,171,000)	(929,000)	(1,171,000)
Deferred tax liabilities, gross	(7,995,000)	(929,000)	(7,995,000)
Deferred Tax Assets, Net	340,156,000	276,555,000	340,156,000
Increase in deferred tax assets			340,200,000
Operating Loss Carryforwards [Line Items]
Utilization of net operating loss carryforwards related to exercises of Nonqualified Stock Options and disqualifying dispositions of ISOs, credited to additional paid-in capital		216,857,000	4,308,000
Effective Income Tax Rate Reconciliation, Tax Credit, Research, Amount		34,000,000
Income Tax Reconciliation, Change in Deferred Tax Assets Valuation Allowance			340,200,000
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	8,400,000	23,500,000	8,400,000	4,200,000
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued		0
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Estimated Range of Change, Upper Bound		8,000,000
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance as of January 1		11,274,000	5,596,000	12,819,000
Gross increases related to current year tax positions		7,620,000	1,873,000	2,192,000
Gross increases related to prior year tax positions		8,305,000	3,805,000	0
Gross decrease due to settlements, recapture, filed returns, and lapse of statutes of limitation		(572,000)	0	(9,415,000)
Balance as of December 31	11,274,000	26,627,000	11,274,000	5,596,000
U.S. Federal and New York State
Operating Loss Carryforwards [Line Items]
Operating loss carry-forwards		$ 450,400,000