Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of provision for income taxes
Current income tax expense			$ 81,689	$ 109,727	$ 106,155
Deferred income tax expense (benefit)			26,912	(2)	(14,584)
Other income tax expense			10,095
Income tax expense			$ 118,696	$ 109,725	$ 91,571
Federal statutory income tax rate
Corporate tax rate			35.00%
Tax Cuts and Jobs Act of 2017
Schedule of provision for income taxes
Other income tax expense	$ 10,100		$ 10,100
Tax Cuts and Jobs Act of 2017 | Scenario, Forecast
Federal statutory income tax rate
Corporate tax rate		21.00%