Income Taxes (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Operating Loss Carryforwards [Line Items]
Total income tax expense (benefit)	$ 96,358,000	$ 84,378,000	$ 316,562,000	$ 187,651,000
Effective income tax rate	54.70%	37.40%	57.10%	36.40%
Effective Income Tax Rate Reconciliation, Change in Tax Rates, Percent			2.20%
Effective Income Tax Rate Reconciliation, Tax Credit, Research, Percent				4.30%
Available-for-sale Securities, Income Tax Expense on Change in Unrealized Holding Gain (Loss)	$ 13,500,000	$ 0	$ 14,900,000	$ 0
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Effective income tax rate			0.00%