Income Taxes (Details) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Operating Loss Carryforwards [Line Items]
Total income tax expense (benefit)	$ 164,415,000	$ 200,502,000
Effective income tax rate	49.80%	72.50%
Available-for-sale Securities, Income Tax Expense on Change in Unrealized Holding Gain (Loss)	$ 2,000,000.0	$ 2,500,000.0