Income Taxes (Schedule of Components of Income Tax Expense (Benefit) ) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Taxes
Current income tax expense	$ 304,726	$ 269,387	$ 153,176
Deferred income tax expense (benefit)	59,243	(139,948)	50,951
Total income tax expense	$ 363,969	$ 129,439	$ 204,127