Income Taxes (Details) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating Loss Carryforwards [Line Items]
Total income tax expense (benefit)	$ 183,358,000	$ 148,766,000
Effective income tax rate	42.40%	45.10%
Available-for-sale Securities, Income Tax Expense on Change in Unrealized Holding Gain (Loss)	$ 0	$ 2,000,000.0