Income Taxes (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Components of Income Tax Expense (Benefit), Continuing Operations [Abstract]
Total income tax expense (benefit)	$ 110,384,000	$ 60,316,000	$ 220,204,000	$ 103,273,000
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]
Effective income tax rate	54.30%	40.80%	58.20%	35.70%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent			0.00%
Effective Income Tax Rate Reconciliation, Change in Tax Rates, Percent			3.90%
Operating Loss Carryforwards [Line Items]
Effective Income Tax Rate Reconciliation, Tax Credit, Research, Percent				6.00%
Available-for-sale Securities, Income Tax Expense on Change in Unrealized Holding Gain (Loss)	$ 1,400,000	$ 0	$ 1,100,000	$ 0