Income Taxes (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Operating Loss Carryforwards [Line Items]
Total income tax expense (benefit)	$ 138,106,000	$ 96,038,000	$ 321,464,000	$ 244,804,000
Effective income tax rate	26.30%	32.90%	33.60%	39.30%
Available-for-sale Securities, Income Tax Expense on Change in Unrealized Holding Gain (Loss)				$ 1,600,000.0