Income Taxes (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating Loss Carryforwards [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	$ 775,747,000	$ 713,360,000	$ 414,421,000
Current:
Federal	447,370,000	201,475,000	0
State	28,718,000	23,489,000	4,308,000
Current Foreign Tax Expense (Benefit)	2,879,000	433,000	0
Total current tax expense (benefit)	478,967,000	225,397,000	4,308,000
Deferred:
Federal	(68,700,000)	54,910,000	(300,319,000)
State	18,891,000	8,700,000	(39,837,000)
Deferred Foreign Income Tax Expense (Benefit)	(1,485,000)	(9,000)	0
Total deferred tax expense (benefit)	(51,294,000)	63,601,000	(340,156,000)
Total income tax expense (benefit)	427,673,000	288,998,000	(335,848,000)
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	2.00%	3.40%	5.40%
Change in state effective rate	2.80%	0.00%	5.40%
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Percent	15.30%	4.90%	0.00%
Effective Income Tax Rate Reconciliation, Tax Credit, Percent	(7.40%)	(4.90%)	0.00%
Reclassification of net operating losses related to exercises of stock options	0.00%	0.00%	9.30%
Provision (benefit) attributable to valuation allowances	0.00%	0.00%	(139.00%)
Effective Income Tax Rate Reconciliation, Tax Contingency, Domestic, Percent	2.50%	0.00%
Effective Income Tax Rate Reconciliation, Deduction, Medicare Prescription Drug Benefit, Percent	2.70%	1.10%	0.00%
Other permanent differences	2.20%	1.00%	2.80%
Effective income tax rate	55.10%	40.50%	(81.10%)
Deferred tax assets:
Net operating loss carry-forward	150,000	135,000
Fixed assets	8,078,000	18,902,000
Deferred revenue	75,503,000	88,033,000
Deferred compensation	194,489,000	109,715,000
Income tax credit carry-forwards	16,099,000	9,372,000
Capitalized research and development costs	12,908,000	18,942,000
Other	41,252,000	34,215,000
Deferred tax assets, gross	348,479,000	279,314,000
Valuation allowance	(359,000)	(1,830,000)
Deferred tax assets, net	348,120,000	277,484,000
Deferred tax liabilities:
Accruals	(28,186,000)	0
Convertible senior notes	(252,000)	(929,000)
Deferred Tax Liabilities, Other	3,578,000	0
Deferred tax liabilities, gross	(32,016,000)	(929,000)
Deferred Tax Assets, Net	316,104,000	276,555,000
Utilization of net operating loss carryforwards related to exercises of Nonqualified Stock Options and disqualifying dispositions of ISOs, credited to additional paid-in capital	448,556,000	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	51,200,000	23,500,000	8,400,000
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued		0
Other Comprehensive Income (Loss), Tax	27,100,000	0	0
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance as of January 1	26,627,000	11,274,000	5,596,000
Gross increases related to current year tax positions	27,538,000	7,620,000	1,873,000
Gross increases related to prior year tax positions	6,464,000	8,305,000	3,805,000
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities	3,014,000	572,000	0
Balance as of December 31	57,615,000	26,627,000	11,274,000
UNITED STATES
Operating Loss Carryforwards [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	1,115,958,000	812,278,000
Foreign
Operating Loss Carryforwards [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	$ (340,211,000)	$ (98,918,000)